Traxxas 49104-1 User Manual

MODEL 49104-1

owner’s manual

3

BEFORE YOU
PROCEED

4

SAFETY
PRECAUTIONS

5

TOOLS, SUPPLIES,
AND REQUIRED
EQUIPMENT

6

ANATOMY OF
THE T-MAXX

7

QUICK START:
GETTING UP TO
SPEED

8

TRAXXAS TQ 2.4GHz
RADIO SYSTEM

14

THE TRX 2.5
RACING ENGINE

29

DRIVING
YOUR T-MAXX

30

TUNING
ADJUSTMENTS

33

MAINTAINING
AND STORING
YOUR T-MAXX

35

TROUBLESHOOTING
YOUR T-MAXX

2 • T-MAXX

INTRODUCTION

Thank you for purchasing a Traxxas T-Maxx Nitro Monster Truck.
Traxxas engineers have loaded your T-Maxx with innovative features
and incredible “drive-over-anything” performance that you won’t find
anywhere else!

Your T-Maxx combines automatic, two-speed shifting in forward
and reverse, with powerful four-wheel disc braking. The patented
transmission design and

TQ 2.4GHz system put these functions right at

your fingertips.

The TRX 2.5 engine is one of the most powerful engines of its size
ever available in a Ready-To-Race

®

truck. Two years of engineering
development and advanced design, along with thousands of hours of
testing, puts the TRX 2.5 in a class by itself. Each part of the TRX 2.5,
from the air filter on the slide carburetor, to the tip on the dyno-tuned
exhaust system, has been carefully engineered to provide maximum
power over the broadest RPM range.

We know you’re excited about getting your new T-Maxx on
the road, but it’s very important that you take some time to
read through the Owner’s Manual. This manual contains all the
necessary set-up, break-in, tuning, and operating procedures that
allow you to unlock the incredible performance and adjustment
potential that Traxxas engineers designed into T-Maxx. Even if you

are an experienced R/C enthusiast, it’s important to read and
follow the procedures in this manual. Pay particular attention to
the fuel and break-in requirements for the engine. The advanced

design of the TRX Racing Engine has a special break-in procedure
that has been developed and proven to produce the best­performing engine possible. Using traditional or old-fashioned
procedures could reduce engine performance and longevity.

FCC Compliance
This device contains a module that complies with the limits for a Class B digital device as described in part 15 of the FCC rules. Operation is subject to the following two conditions: (1) This device may not
cause harmful interference, and (2) this device must accept any interference received, including interference that may cause undesired operation.

The limits for a Class B digital device are designed to provide reasonable protection against harmful interference in residential settings. This product generates, uses and can radiate radio frequency energy,
and, if not operated in accordance with the instructions, may cause harmful interference to radio communications. The user is cautioned that changes or modifications not expressly approved by the party
responsible for compliance could void the user’s authority to operate the equipment.

Canada, Industry Canada (IC)
This Class B digital apparatus complies with Canadian ICES-003 and RSS-210. This device complies with Industry Canada license exempt RSS standard(s). Operation is subject to the following two conditions:
This device may not cause interference, and This device must accept any interference, including interference that may cause undesired operation of the device.

Radio Frequency (RF) Exposure Statement
This equipment complies with radio frequency exposure limits set forth by FCC and Industry Canada for an uncontrolled environment. This equipment should be installed and operated with a minimum
distance of 20 centimeters between the radiator and your body or bystanders and must not be co-located or operated in conjunction with any other antenna or transmitter.

Traxxas Support

Traxxas support is with you every step of the
way. Refer to the next page to find out how to
contact us and what your support options are.

Quick Start

This manual is designed with a Quick
Start path that outlines the necessary
procedures to get your model up
and running in the shortest time possible. If you are an
experienced R/C enthusiast, you will find it helpful and fast.
Be sure and read through the rest of the manual to learn
about important safety, maintenance, and adjustment
procedures. Turn to page 7 to begin.

T-Maxx is made to be a complete package that starts with the
highest level of engineering and is equipped stock with one of the
most powerful Ready-To-Race

®

engines available. We want you
to feel confident that you own the best-performing truck in the
market and that it is backed by a team of professionals who aim
to provide the highest level of factory support possible. T-Maxx
is about experiencing total performance and satisfaction, not just
with your truck, but also with the company that stands behind it.

Thank you again for going with Traxxas. We work hard every day
to ensure you receive the highest level of customer satisfaction
possible. We truly want you to enjoy your new T-Maxx!

BEFORE YOU PROCEED

Carefully read and follow all instructions in this and any accompanying
materials to prevent serious damage to your model. Failure to follow
these instructions will be considered abuse and/or neglect.

Before running your model, look over this entire manual and examine
the truck carefully. If for some reason you decide the T-Maxx is not
what you wanted, then do not continue any further. Your hobby
dealer absolutely cannot accept a T-Maxx for return or exchange after
it has been run.

WARNINGS, HELPFUL HINTS, & CROSS-REFERENCES

Throughout this manual, you’ll notice warnings and helpful hints
identified by the icons below. Be sure to read them!

An important warning about personal safety or avoiding
damage to your model and related components.

Special advice from

Traxxas to make things easier and more fun.

Refers you to a page with a related topic.

SUPPORT

If you have any questions about your model or its operation,
call the Traxxas Technical Support line toll-free at:

1-888-TRAXXAS (1-888-872-9927)

*

Technical support is available Monday through Friday from 8:30 am
to 9:00 pm central time. Technical assistance is also available at
Traxxas.com. You may

also e-mail customer support with your
question at [e-mail]. Join thousands of registered
members in our online community at Traxxas.com.

Traxxas offers a full-service, on-site repair facility to handle any of
your Traxxas service needs. Maintenance and replacement parts may
be purchased directly

from Traxxas by phone or online at BuyTraxxas.
com. You can save time, along with shipping and handling costs, by
purchasing replacement parts from your local dealer.

Do not hesitate to contact us with any of your product support needs.
We want you to be thoroughly satisfied with your new model!

REGISTERING YOUR MODEL

In order to serve you better as our customer, please
register your product within 10 days of your purchase
online at Traxxas.com/register.

Traxxas.com/register

Traxxas
6200 Traxxas Way
McKinney, TX 75070
Phone: [phone]
Toll-free 1-888-TRAXXAS

Internet
Traxxas.com
E-mail: [e-mail]

Entire contents ©2014 Traxxas.
Traxxas, Maxx, T-Maxx, TRX 2.5
Racing Engine, TQ, Top Fuel,
EZ-Start, Ready-To-Race, Ready-To­Win, and ProGraphix are trademarks
or registered trademarks of Traxxas.
Other brand names and marks are
the property of their respective
holders and are used only for
purposes of identification. No part
of this manual may be reproduced
or distributed in print or electronic
media without the express written
permission of Traxxas. Specifications
are subject to change without
notice.

*Toll-free support is available to U.S. residents only.

T-MAXX • 3

SAFETY PRECAUTIONS

Choose the Model That is Right For You. For individual Models

No previous experience with radio controlled models is required.
Models require a minimum of setup, maintenance, or support equipment.

Previous experience with radio controlled models is recommended.
Models require a higher level of setup, maintenance, or support equipment.

No previous experience with radio controlled models is required.
Model requires a minimum of setup, maintenance, or support equipment.

Previous experience with radio controlled models is recommended.
Model requires a higher level of setup, maintenance, or support equipment.

BELOW TEXT HAS BEEN UPDATED on 3-14-07
Kent wants maintenance text to be at the END of the paragraph.-- KB

All instructions and
precautions outlined in this
manual should be strictly
followed to ensure safe
operation of your model.

This model is not intended
for use by children (minors)
under 16 years of age
without the supervision
of a responsible and
knowledgeable adult.

Previous experience with
radio controlled models is
mandatory. These models
are capable of high speeds,
requiring experienced
driving control. Models
require detailed setup,
and/or maintenance
procedures with required
support equipment.

4 • T-MAXX

All of us at Traxxas want you to safely enjoy your new T-Maxx. Operate your T-Maxx
sensibly and with care, and it will be exciting, safe, and fun for you and those
around you. Failure to operate your T-Maxx in a safe and responsible manner may
result in property damage and serious injury. The precautions outlined in this
manual should be strictly followed to help ensure safe operation. You alone must
see that the instructions are followed and the precautions are adhered to.

IMPORTANT POINTS TO REMEMBER

• T-Maxx is very fast! The T-Maxx is intended for experienced users with a
high level of skill. The TRX 2.5 Racing Engine is extremely powerful and may
require skilled driving to maintain control. Children under 16 years of age and
inexperienced drivers should not operate the T-Maxx without the supervision of
a responsible and knowledgeable (experienced) adult.

• Model engine fuel is dangerous and highly poisonous. Always follow all
directions and precautions printed on the fuel container. Model engine fuel is
poisonous to humans and animals. Drinking the fuel can cause blindness and
death. Handle with care and respect.

• Model engine fuel, especially when in a fuel dispensing bottle, may look like a
cool drink to a child. Keep all fuel out of the reach of children at all times. Do

not place fuel containers on the ground where children can reach them while
you are driving.

• Model engine fuel is flammable. Never allow smoking, sparks, heat, or flame in
the presence of fuel or fuel vapors.

• The engine, brakes, and exhaust system may become extremely hot during use. Be
careful not to touch these parts, especially when refueling or stopping the engine.

• Prolonged exposure to the engine exhaust can be harmful. Avoid breathing
the engine exhaust. Always run your T-Maxx outdoors, in a well-ventilated area.
Never run the engine indoors.

• Do not operate your T-Maxx at night, or anytime your line of sight to the model
may be obstructed or impaired in any way.

• Never operate your T-Maxx in crowds of people or busy pedestrian areas.
T-Maxx is very fast and could cause injury to those unaware of its presence.
Keep small children at a safe distance away from the operating area.

• Because T-Maxx is controlled by radio, it is subject to radio interference
from many sources beyond your control. Since radio interference can cause
momentary loss of control, always allow a safety margin in all directions around
your model to prevent collisions.

• The engine can be loud. If the noise makes you uncomfortable, wear ear
protection. Be considerate of your neighbors by not running your model early
in the morning or late in the evening.

• Do not cut the antenna “stinger” or any other part of the antenna wire. Cutting
the antenna will reduce range.

• Do not kink the antenna wire. Kinks in the antenna wire will reduce range.

• You must extend the antenna wire in the model as far as possible for maximum
range. In doing so, the antenna wire will be extended outside of the vehicle body.
Do not wrap or coil the antenna wire to keep it from extending out of the body.

• Do not allow the antenna wire to extend outside the body without the
protection of an antenna tube, or the antenna wire may incur crash damage

1

that could reduce range.

• Most importantly, use good common sense at all times.

BATTERIES AND BATTERY CHARGING

Your model uses rechargeable batteries that must be handled with care for
safety and long battery life. Make sure to read and follow all instructions and
precautions that were provided with the battery packs and your charger. It is your
responsibility to charge and care for the battery packs properly. In addition to
your battery and charger instructions, here are some more tips to keep in mind.

• Use the supplied charger to charge the included battery. See “Charging the EZ-
Start Battery” on page 21.

• Do not charge batteries inside of an automobile. Do not charge batteries while
driving in an automobile. The charger is equipped with a long cord intended
to allow the battery to be charged outside of an automobile when using the
automobile’s auxiliary power socket. If the cord will not reach outside of the
automobile, find another power source.

• Never leave batteries to charge unattended.

• Allow the battery pack to cool off before charging.

• Do not use battery packs that have been damaged in any way. Do not use
battery packs that have damaged wiring, exposed wiring, or a damaged
connector as this may create the risk of fire.

• Children should have responsible adult supervision when charging and
handling batteries.

• Never charge batteries on wood, cloth, carpet or on any other flammable
material.

• Do not operate the charger in a cluttered space, or place objects on top of the
charger or battery.

• If a battery gets hot to the touch during the charging process (temperature
greater than 140°F / 60°C), disconnect the battery from the charger and
discontinue charging immediately.

• Always store battery packs safely out of the reach of children and pets.

• Do not expose the charger to water or moisture.

• Do not disassemble the charger.

• Only use approved chargers for Nickel Metal Hydride (NiMH) battery packs. Do
not exceed the maximum charge rate of 1 amp.

• Do not short-circuit the battery pack. This may cause burns and severe damage
to the battery pack.

• Do not burn or puncture the batteries. Toxic materials could be released. If eye
or skin contact occurs, flush with water.

• Store the battery pack in a dry location, away from heat sources and direct
sunlight.

• NiMH batteries must be recycled or disposed of properly.

Recycling Your Traxxas Power Cell NiMH Battery

Traxxas strongly encourages you to recycle your Power Cell NiMH battery when it
has reached the end of its useful life. Do not throw your battery in the trash. All
Power Cell NiMH battery packs display the RBRC (Rechargeable Battery Recycling
Corporation) icon, indicating they are recyclable. To find a recycling center near
you, ask your local hobby dealer or visit www.call2recycle.org.

TOOLS, SUPPLIES, AND REQUIRED EQUIPMENT

T-Maxx comes with a set of specialty metric tools. You’ll need to purchase other items, available from your hobby dealer, to operate and maintain your model.

SUPPLIED TOOLS AND EQUIPMENT

For more information on radio
system batteries, see Use the
Right Batteries on page 10.

Turnbuckle wrenches

1.5mm “L” wrench

battery pack*

U-joint wrench

2.0mm “L” wrench

NiMH 7.2V battery

charger*

REQUIRED TOOLS AND EQUIPMENT

10% quart - #5010
20% quart - #5020
33% quart - #5030
10% gallon - #5060
20% gallon - #5070
33% gallon - #5080

Traxxas Top Fuel

see page 18

™

8 AA alkaline batteries

4-way wrench

2.5mm “L” wrench 5.0mm “L” wrench

Fuel dispensing bottleNiMH 7.2V

(sold separately)

After-run oil to protect

the engine from corrosion

Antenna nut wrench

Small flat-blade screwdriver

for tuning (1/8 inch blade)

Extra

glow plug

Glow plug and

wheel nut wrench

Foam air filter oil and

extra oiled air filter element

(see page 19)

Recommended Equipment

These items are not required
for the operation of your
model, but are a good idea to
include in any R/C toolbox:

• Safety glasses

• Traxxas Ultra Premium Tire
Glue, part #6468 (CA glue)

• Hobby knife

• Side cutters and/or
needle nose pliers

• Philips screwdriver

• Soldering iron

*Battery and charger style are subject to change and may vary from images.

T-MAXX • 5

ANATOMY OF THE T-MAXX

Fuel Tank

Fuel Tank Lid

Fuel Line

EZ-Start Motor

Pressure Line

EZ-Start Plug

Bumper Mount

Body Mount

Shift Rod

On/Off Switch

Battery Box

Slipper Clutch

Spur Gear

Two Speed
Adjustment
Access Plug

Steering Servo

Shifting Servo

Suspension Arm

(upper)

Throttle/Brake Servo

Shock Tower

Bumper (front)

Skid Plate (front)

Cross-brace

Differential

TRX 2.5 Racing Engine

see pg. 15 for details

Header

Driveshaft
(Half Shaft)

6 • T-MAXX

Bulkhead

Transmission

Air Filter

Oil Shock (Damper)

Pipe Hanger

Tuned Pipe

Receiver Box

Chassis

Antenna Mount

Toe Link

(Turnbuckle)

QUICK START: GETTING UP TO SPEED

The following guide is an overview of the procedures for getting your T-Maxx running, from opening the box to breaking in and tuning your
engine. Refer to the pages indicated for details on each step. Look for the Quick Start logo on the bottom corners of Quick Start pages.

1. Read the safety precautions on page 4

For your own safety, understand where carelessness and misuse could
lead to personal injury.

2. Charge the EZ-Start battery pack • See page 22

The EZ-Start requires a fully charged 7.2-volt battery pack (included). Use your fuel-dispensing bottle to fill the tank.

3. Install the antenna • See page 10

The receiver antenna and antenna tube must be properly installed
before operating your model.

4. Install batteries in the transmitter • See page 10

T-Maxx requires 4 AA alkaline or rechargeable batteries*
for the transmitter.

5. Decal and Install the body • See page 8

You will need to use the body during break in, so it’s best to apply any
additional decals before you use the body.

10. Range test the radio system • See page 12

Follow this procedure to make sure your radio system works properly at
a distance and that there is no interference from outside sources.

11. Fill the fuel tank • See page 19

12. Connect the EZ-Start to the model • See page 22

Learn the proper way to use the EZ-Start electric starting system.

13. Start the engine • See page 24

Learn to use

the correct starting procedure for your TRX 2.5.

14. Break-in your engine • See page 24

Follow the break-in instructions exactly to ensure the
best-performing, longest-lasting engine.

The Quick Start Guide is
not intended to replace the
full operating instructions
available in this manual.
Please read this entire
manual for complete
instructions on the proper
use and maintenance of
your T-Maxx.

6. Install the receiver batteries • See page 10

T-Maxx requires 4 AA alkaline or rechargeable batteries* for
the receiver.

7. Install the EZ-Start battery • See page 22

Install and connect a charged 7.2-volt battery pack in
the EZ-Start controller.

8. Turn on the radio system • See page 11

15. Tune your engine • See page 26

Learn how to

set the fuel mixture needles for optimum

engine performance.

16. Drive your T-Maxx • See page 29

Learn to use

the two-speed and reverse functions on your truck, along

with important driving precautions.

17. Maintain your Truck • See pages 33-34

Make a habit of turning the transmitter on first and off last. Follow these critical steps to maintain the performance of your

T-Maxx and keep it in excellent running condition.

9. Check servo operation • See page 12

Make sure the throttle, shifting, and steering servos are
working correctly.

*sold separately

Look for the Quick Start
logo at the bottom of
Quick Start pages.

T-MAXX • 7

K
A

1
8

6
7

­R

0
0

KA1867-R00

Applying The Decals

The main decals for your model
have been applied at the
factory. Additional decals are
printed on self-adhesive clear
mylar and are die-cut for easy
removal. Use a hobby knife
to lift the corner of a decal
and lift it from the backing.

TRAXXAS TQ 2.4GHz RADIO SYSTEM

Your model is equipped with the Traxxas TQ 2.4GHz transmitter. The transmitter has three channels: Channel one operates the steering,
channel two operates the throttle, and channel three operates shifting. The receiver inside the model has three output channels. Your
model is equipped with three servos and a receiver.

TQ 2.4GHz TRANSMITTER

Steering Wheel

Red/Green Status LED

Set Button

WIRING DIAGRAM

To apply the decals, place one
end down, hold the other end
up, and gradually smooth the
decal down with your finger
as you go. This will prevent air
bubbles. Placing both ends of
the decal down and then trying
to smooth it out will result in
air pockets.

8 • T-MAXX

4-Cell
Battery Holder

Steering
Trim

Antenna

On/Off
Switch

Receiver

Shifting
Switch

CH3 - Shifting Servo
CH2 - Throttle Servo
CH1 - Steering Servo

Throttle
Trigger

CH1 - Battery

Channel 3
Shifting Servo

Channel 2

Power Switch Battery Compartment

Throttle Servo

Channel 1
Steering Servo

5

TRAXXAS TQ 2.4GHz RADIO SYSTEM

INTRODUCTION

Your model includes the TQ 2.4GHz transmitter. When powered
on, the TQ will automatically locate and lock onto an available
frequency, allowing multiple models to be raced together without
frequency conflicts. Just switch on and drive! The included TQ

2.4GHz radio system has been programmed for your model at the
factory and does not require adjustment, but it does have settings
you may need to access to maintain proper operation of your
model. The detailed instructions (page 11) included in this manual
will help you understand and operate the functions of the new
TQ 2.4GHz radio system. For additional information and how-to
videos, visit Traxxas.com.

RADIO SYSTEM TERMINOLOGY

Please take a moment to familiarize yourself with these radio and
power system terms. They will be used throughout this manual.

2.4GHz Spread Spectrum – This model is equipped with the
latest R/C technology. Unlike AM and FM systems that require
frequency crystals and are prone to frequency conflicts, the TQ

2.4GHz system automatically selects and locks onto an open
frequency, and offers superior resistance to interference and
“glitching.”

Current – Current is a measure of power flow through the

electronics, usually measured in amps. If you think of a wire as a
garden hose, current is a measure of how much water is flowing
through the hose.

Frequency band – The radio frequency used by the transmitter to

send signals to your model. This model operates on the 2.4GHz
direct-sequence spread spectrum.

mAh – Abbreviation for milliamp hour, a measure of the capacity

of the battery pack. The higher the number, the longer the
battery will last between recharges.

Neutral position – The standing position that the servos seek

when the transmitter controls are at the neutral setting.

NiCad – Abbreviation for nickel-cadmium. The original

rechargeable hobby pack, NiCad batteries have very high
current handling, high capacity, and can last up to 1000
charging cycles. Good charging procedures are required to
reduce the possibility of developing a “memory” effect and
shortened run times.

NiMH – Abbreviation for nickel-metal hydride. Rechargeable

NiMH batteries offer high-current handling and much greater
resistance to the “memory” effect. NiMH batteries generally
allow higher capacity than NiCad batteries. They can last up to
500 charge cycles. A peak charger designed for NiMH batteries is
required for optimal performance.

Receiver – The radio unit inside your model that receives signals

from the transmitter and relays them to the servos.

Servos – Small motor units in your model that operate the steering

and throttle mechanisms.

Transmitter – The hand-held radio unit that sends throttle and

steering instructions to your model.

Trim – The fine-tuning adjustment of the neutral position of the

servos, made by adjusting the steering trim knob on the face of
the transmitter.

2-channel radio system – The TQ radio system, consisting of the

receiver, the transmitter, and the servos. The system uses two
channels: one to operate the throttle and one to operate the
steering.

RADIO SYSTEM PRECAUTIONS

• Do not kink the receiver antenna wire. Kinks in the antenna wire
will reduce range.

• DO NOT CUT any part of the receiver antenna wire. Cutting the
antenna will reduce range.

• Extend the antenna wire in the model as far as possible for
maximum range. In doing so, the antenna wire will be extended
outside of the vehicle body. Do not wrap or coil the antenna wire
to keep it from extending out of the body.

• The antenna wire must be installed into the antenna tube to
protect it from getting cut or damaged, which will reduce range.
When installing the antenna wire into the antenna tube, be
careful not to kink the wire by pressing it against the antenna
tube cap. The antenna wire should extend to just below or to
within one-half inch below the cap.

Learn terms related to
the TRX 2.5 Racing Engine
beginning on page 16.

T-MAXX • 9

TRAXXAS TQ 2.4GHz RADIO SYSTEM

To prevent loss of radio range,
do not kink or cut the black wire,
do not bend or cut the metal tip,
and do not bend or cut the white
wire at the end of the metal tip.

Correct

NoNo NoNo

Use the Right Batteries

Your transmitter uses AA
batteries. Use new alkaline
batteries or rechargeable
batteries in your transmitter.
Make sure rechargeable
batteries are fully
charged according to the
manufacturer’s instructions.

If you use rechargeable
batteries in your transmitter,
be aware that when they
begin to lose their charge,
they lose power more
quickly than regular alkaline
batteries.

Caution: Discontinue running
your model at the first sign of
weak batteries (flashing red
LED) to avoid losing control.

10 • T-MAXX

3,4,6

INSTALLING THE RECEIVER ANTENNA

The receiver antenna and antenna tube must
be properly installed before operating your
model. The antenna tube has been precisely
cut to match the length of the antenna wire.
Follow these steps to install the antenna and
antenna tube:

1. Slide the antenna wire into the antenna
tube until the antenna’s white tip just
reaches the tube cap. Do not crush the
antenna wire against the cap.

2. Insert the tube into the antenna post. Take
care not to crimp the antenna wire.

3. Slide the crimp nut over the antenna tube
and thread it onto the antenna post. Use
the supplied tool to thread the crimp nut
over the post until the antenna tube is
secure. Do not over-tighten the nut or
crush the antenna wire against the chassis.
Do not bend or kink the antenna wire! Do
not shorten the antenna tube. See the side

bar for more information.

Antenna

Tip

Antenna

Tube

Antenna

Wrench

Antenna

Crimp Nut

Antenna

Post

INSTALLING RECEIVER BATTERIES

The radio receiver in your T-Maxx uses 4 AA batteries. The battery
holder for the receiver batteries is located underneath the battery
cover. The battery cover can be identified by the on/off switch.

1. Remove the battery cover
by removing the two
3x10mm buttonhead
cap screws from the
cover.

2. Remove the battery
holder and install 4 AA
alkaline batteries. Make
careful note of the battery
polarity by comparing
against the diagrams in the
battery holder.

3. Insert the battery holder into the battery cover.

4. Direct the battery wires through the slot
in the battery cover. Note: If the wires

are not properly routed, they may
become broken or shorted, causing
radio system failure and loss of control.

5. Reinstall the battery cover and secure
with the screws.

To prevent losing control of your model, it is important to stop
at the first sign of weak receiver batteries. Visible warning signals
include sluggish steering response and shortened radio range.

INSTALLING TRANSMITTER BATTERIES

Your TQ 2.4GHz transmitter uses 4 AA batteries. The battery
compartment is located in the base of the transmitter.

1. Remove the battery
compartment door by
pressing the tab and
sliding the door open.

2. Install the batteries
in the correct
orientation as
indicated in
the battery
compartment.

3. Reinstall
the battery
compartment door and snap it closed.

4. Turn on the transmitter and check
the status LED for a solid green light.

If the status LED flashes red, the transmitter batteries may be weak,
discharged, or possibly installed incorrectly. Replace with new
or freshly charged batteries. The power indicator light does not
indicate the charge level of the battery pack installed in the model.
Refer to the LED Codes section on page 13 for more information on
the transmitter’s status LED codes.

TRAXXAS TQ 2.4GHz RADIO SYSTEM

RADIO SYSTEM CONTROLS

T

U

R

N

R

I

G

H

T

T

Neutral

Brake

Forward

Reverse

Forward

T

U

R

N

L

E

F

RADIO SYSTEM RULES

• Always turn your TQ 2.4GHz transmitter on first and off last. This
procedure will help to prevent your model from receiving stray
signals from another transmitter, or other source, and running
out of control. Your model has electronic fail-safes to prevent this
type of malfunction, but the first, best defense against a runaway
model is to always turn the transmitter on first and off last.

1

Always turn your

transmitter on first.

2

Always turn your

receiver on second.

Then start your engine.

• In order for the transmitter and receiver to bind to one another,
the receiver in the model must be turned on within 20 seconds
of turning on the transmitter. The transmitter LED will flash fast
red, indicating a failure to link. If you miss it, simply turn off the
transmitter and start over.

3

• Always have the transmitter and receiver turned on before you
start the engine. Never turn the radio system off while the engine
is running. The on/off switch in the model only turns the receiver
on and off. It does not turn off the engine.

• Always use new or freshly charged batteries for the radio system.
Weak batteries will limit the radio signal between the receiver
and the transmitter. Loss of the radio signal can cause you to lose
control of your model.

RADIO SYSTEM BASIC ADJUSTMENTS

Steering Trim

The steering trim knob located on the face of the
transmitter adjusts the neutral (center) point of the

when the steering wheel is centered, turn the knob until the model
drives straight when the steering wheel is centered.

Servo Reversing
The TQ transmitter has been programmed with the correct servo
direction settings for your model and should not require adjustment.

These instructions are for reference and troubleshooting only.

Reversing a channel reverses the direction of the corresponding
servo. For example, if you turn the steering wheel to the right and
the model turns left, Channel 1 would need to be reversed to correct
the servo direction. Use the following procedures to reverse the
steering or throttle channel if necessary. Servo reversing should only

be required if you accidentally reset the direction of a channel. Do not
reverse the throttle or steering channels unless necessary.

Note

transmitter and receiver are powered on.

Steering reversing procedure:

1. Press and hold the SET button on the transmitter for two

seconds. The status LED will flash green.

2. Turn and hold the steering wheel to the full left or full right

position (it does not matter which position you choose).

3. While holding the steering wheel in position, press the SET

button to reverse the channel.

4. The channel is now reversed. Confirm correct servo operation

before running your model.

steering channel. If your model pulls to the right or left

: Before performing these procedures, make sure that both the

Remember to always turn the
TQ transmitter on first and off
last to avoid loss of control
and damage to your model.

If the status LED doesn’t light
green, check the polarity of the
batteries. Check rechargeable
batteries for a full charge. If
you see any other flashing
signal from the status LED,
refer to the chart on page 13 to
identify the code.

Make certain the model’s
receiver antenna is properly
installed before operating
your model. See “Installing
the Receiver Antenna.” Failure

to properly install the receiver
antenna will result in greatly
reduced radio range and
potential loss of control.

8

T-MAXX • 11

TRAXXAS TQ 2.4GHz RADIO SYSTEM

Always use the idle speed
adjustment screw (see page 21)
on the carburetor (see page 15) to
adjust the engine idle speed.

12 • T-MAXX

9, 1 0

Throttle reversing procedure:

1. Press and hold the SET button on the transmitter for two
seconds. The status LED will flash green.

2. Move and hold the throttle trigger to the full forward or full
brake position.

3. While holding the throttle trigger in position, press the SET
button to reverse the channel.

4. The channel is now reversed. Confirm correct servo operation
before running your model.

Warning: Changing the direction of the throttle servo will also

change its neutral position. Be certain to confirm the throttle servo
properly closes the engine’s throttle opening when the transmitter’s
trigger is at neutral.

USING THE RADIO SYSTEM

The TQ 2.4GHz Radio System has been adjusted at the factory for
correct operation with your model. The adjustment should be
checked before running the model, in case of movement during
shipping. Follow these steps:

1. Turn the transmitter switch on. The status LED on the

transmitter should be solid green (not flashing).

2. Turn on the receiver switch in the model. The switch is located

on the battery compartment.

3. Position T-Maxx so that its front wheels are off the ground.

4. Turn the steering wheel on the transmitter back and forth

and check for rapid operation of the steering servo. Also,
check that the steering mechanism is not loose or binding. If
the steering operates slowly, then make sure you have fresh
receiver batteries.

5. When looking down at the

model, the front wheels should
be pointing straight ahead. If
the wheels are turned slightly
to the left or right, slowly adjust
the steering trim control on the
transmitter until they are pointing straight ahead.

6. Operate the throttle trigger on the transmitter and check for

rapid operation of the throttle servo. When the throttle trigger
is pulled back, the carburetor should open (slide moves out).
When the throttle trigger is pushed all the way forward, the
brake should lock.

0°0°

7. Operate the shift button on the transmitter and check for
rapid operation of the shifting servo. Push the shift button
down for forward. The servo will operate the spring-loaded
shift mechanism and you will hear the transmission click into
forward. Push the shift button up for reverse and you will again
hear the transmission click and shift into gear.

8. Once adjustments are made, turn off the receiver on your
T-Maxx, followed by the hand-held transmitter.

The TQ transmitter has a directional antenna. For maximum
range, hold the antenna upright and pointed in the direction
of the model. Pointing the transmitter away from the model
will reduce radio range.

Range-Testing the Radio System

Before each running session with your model, you should range-test
your radio system to ensure that it operates properly.

1. Turn on the radio system and check its operation as described in

the previous section.

2. Have a friend hold the model with the engine off.

3. Walk away from the model with the transmitter until you reach

the farthest distance you plan to operate the model.

4. Operate the controls on the transmitter once again to be sure that

the model responds correctly.

5. Do not attempt to operate the model if there is any problem with

the radio system or any external interference with your radio
signal at your location.

Higher Speeds Require Greater Distance

The faster you drive your model, the more quickly it will near the
limit of radio range. At 50mph, a model can cover 73 feet every
second! It’s a thrill, but use caution to keep your model in range.
If you want to see your model achieve its maximum speed, it is
best to position yourself in the middle of its running area, not the

TRAXXAS TQ 2.4GHz RADIO SYSTEM

far end, so you drive the model toward and past your position. In
addition to maximizing the radio’s range, this technique will keep
your model closer to you, making it easier to see and control.

No matter how fast or far you drive your model, always leave
adequate space between you, the model, and others. Never drive
directly toward yourself or others.

TQ 2.4GHz Binding Instructions

For proper operation, the transmitter and receiver must be
electronically ‘bound.’ This has been done for you at the factory.
Should you ever need to re-bind the system or bind to an additional
transmitter or receiver, follow these instructions. Note: the receiver
must be connected to a 4.8-6.0v (nominal) power source for binding
and the transmitter and receiver must be within 5 feet of each other.

1. Press and hold the SET button on the transmitter.

2. Turn on the transmitter and release the SET button. The status
LED will flash red slowly, indicating that the transmitter is in
bind mode.

3. Press and hold the LINK button on the receiver.

4. Turn on the vehicle and release the LINK button. The LED on the
receiver will flash red, indicating that the receiver is in bind mode.

5. When the LEDs on both the transmitter and the receiver turn solid
green, the system is bound and ready for use. Confirm that the
steering and throttle operate properly before driving your model.

TRANSMITTER LED CODES

LED Color / Pattern Name Notes

Solid green Normal Driving

Slow red
(0.5 sec on / 0.5 sec off)

Flashing medium red
(0.25 sec on / 0.25 sec off)

Flashing fast red
(0.125 sec on / 0.125 sec off)

Mode

Binding

Low Battery
Alarm

Link Failure /
Error

See page 11 for information
on how to use the transmitter
controls.

See this page for more information
on binding.

Put new batteries in the
transmitter. See page 10 for
more information.

Transmitter and receiver are no
longer bound. Turn the system
off and then back on to resume
normal operation. Find source of
the link failure (i.e., out of range,
low batteries, damaged antenna).

RECEIVER LED CODES

LED Color / Pattern Name Notes

Solid green Normal Driving

Slow red
(0.5 sec on / 0.5 sec off)

Flashing fast red
(0.125 sec on / 0.125 sec off)

Mode

Binding

Fail-Safe / Low­Voltage Detect

See page 11 for information
on how to use your transmitter
controls.

See this page for more information
on binding.

Consistent low voltage in the
receiver triggers Fail-Safe so
that there is enough power to
center the throttle servo before it
completely loses power.

Fail-Safe

Your Traxxas radio system
is equipped with a built­in Fail-Safe function that
returns the throttle to its
last saved neutral position
in the event of a signal loss.
The LED on the transmitter
and on the receiver will
rapidly flash red when the
Fail-Safe mode is activated. If
Fail-Safe activates while you
are operating your model,
determine the reason for
signal loss and resolve the
problem before operating
your model again.

T-MAXX • 13

Traxxas strongly discourages
changing or modifying any
part of the TRX 2.5 Racing
Engine. Old tech tips and
tricks that may have boosted
the power of other engines
could seriously diminish the
performance of the
TRX 2.5 Racing Engine.

There’s more advanced
thinking, development,
and testing in the stock
parts of your TRX 2.5
Racing Engine than in many
aftermarket manufacturer’s
performance parts. The TRX

2.5 Racing Engine is already
the most powerful engine
in its class and may not
benefit from average, low­tech, aftermarket bolt-on
performance items.

THE TRX 2.5 RACING ENGINE

™

introduction

The TRX 2.5 Racing Engine is a specialty high-performance racing
engine. Its impressive performance is the result of years of focused
engineering development and thousands of hours of controlled
testing and rigorous real-world running. It offers unprecedented
power and performance that turns ready-to-run into Ready-To-Race®.

The TRX 2.5 Racing Engine takes a total-system approach. Each
part of the engine, from the air filter to the exhaust tip, is carefully
engineered to work in harmony with other engine components. Each
part complements the next to extract maximum power. The TRX 2.5
Racing Engine is designed to be tolerant of variations in tuning, and
to run successfully through a wide range of variable atmospheric
conditions such as changes in temperature, humidity, and altitude.

In order to get the longest engine life and keep the TRX 2.5 Racing
Engine in top running condition, it is very important to perform
regular routine maintenance. The number one cause of premature

engine wear and failure is lack of care and maintenance!

break-in

The TRX 2.5 Racing Engine is manufactured to exacting tolerances
and requires a specially-designed break-in procedure to accomplish
the final precision fitting of the internal engine components. It is very
important that you follow the new break-in procedure as closely as
possible to achieve the best performance and longest life from your
TRX 2.5 Racing Engine. Engine break-in will take between one and
two hours. Old style break-in procedures, such as idling the engine on
the bench for several tanks of fuel or simply running the engine with
a very rich fuel mixture for the first 4 tanks of fuel, will not achieve the
best results. Follow the easy steps in this manual.

air filter maintenance

A clean air filter is critical for long engine life. Due to the high­performance nature of the TRX 2.5 Racing Engine, a tremendous
amount of vacuum is created to move a large volume of high-velocity
air through the carburetor. Dirt is the worst enemy to your engine.
Clean the air filter after each hour of running to prevent sucking
dirt into the engine. An extra pre-lubed air filter element has been
provided to encourage you to maintain your air filter.

after-run maintenance

Perform after-run maintenance on the engine to prevent corrosion
from building up on the internal engine components. The fuel
naturally attracts moisture, and corrosion can build up very quickly
inside the engine if it is not prevented.

A few minutes spent before and after each time you run your model
will allow you to enjoy it for a long time to come. Read on for more
exciting details about your new engine.

14 • T-MAXX

THE TRX 2.5 RACING ENGINE

TRX 2.5 RACING
ENGINE ILLUSTRATED

Air Filter

Housing

High-Speed Needle

Glow Plug

Fuel Intake

Air Intake

Carburetor

Flywheel

Clutch

Bell

Crankshaft

Wire

Idle Speed

Adjustment

Throttle

Arm

Ground

Wire

Screw

Low-Speed

Needle

EZ-Start

Plug

Negative

Wire

Head Protector

Head (Cylinder head)

EZ-Start

Drive Unit

EZ-Start

Motor

Engine

Mount

Crankcase

EZ-Start

Controller

Pressure

Line

Exhaust

Tip

Tuned Pipe

Positive

Wire

Fuel Line

Fuel Tank

T-MAXX • 15

THE TRX 2.5 RACING ENGINE

16 • T-MAXX

TERMS TO KNOW

You’ll find these Nitro R/C engine terms throughout this section
of the manual.

.15 - .15 or “15” refers to the displacement of the engine. The TRX 2.5

Racing Engine is .15 cubic inches or 2.5 cubic centimeters (cc). The
name “TRX 2.5” is derived from the cc measurement.

ABC - Abbreviation for aluminum, brass, and chrome. Refers to engine

construction that consists of an aluminum piston that slides in a
chrome-plated brass sleeve. The TRX 2.5 uses ABC construction.

Air filter - The air filter sits atop the carburetor and prevents harmful

dust and dirt from entering the engine. Dirt ingestion is the number
one cause of premature engine failure, so the engine should never be
run without the air filter in place.

BDC - Bottom dead center. The bottom-most position of the engine

piston stroke.

Break-in - Break-in is the procedure for running a brand new engine

according to specific instructions. This correctly prepares the engine for
normal running. The break-in procedure can be different for different
makes of engines. Follow the Traxxas directions for break-in exactly.

Carb - Abbreviation for carburetor.

Carburetor - The carburetor atomizes (mixes) the fuel with the air so that

the engine can burn it. There are two types of carburetors; slide carbs
and barrel carbs. The TRX 2.5 uses the superior slide carburetor design.

Clean-out - Cleaning-out is a condition that occurs when the engine is

accelerating and the fuel mixture becomes sufficiently lean to allow
the engine to continue into its upper RPM power band. It is usually
characterized by a noticeable decrease in blue exhaust smoke and a
dramatic increase in engine speed.

Combustion chamber - The combustion chamber is machined into the

bottom of the cylinder head. This is where the glow plug ignites the
fuel. The shape of the combustion chamber is designed to promote
more efficient burning of the fuel.

Connecting rod - The connecting rod transfers the piston motion

to the crankshaft. The TRX 2.5 Racing Engine uses a “knife-edged”
connecting rod. The aerodynamic, sharpened edges allow it to “slice”
through the pressurized air/fuel mixture inside the crankcase.

Crankcase - The engine’s “body” that contains all of the running

mechanical components.

Crankshaft - The main shaft of the engine that holds the

reciprocating assembly.

Cooling fins

- The cooling fins are milled into the cylinder head and
crankcase and cause heat to be drawn away from the engine. Heat
is removed when it dissipates into the air, passing across the cooling
fins. It is important to keep the fins clean of dirt and debris for
maximum cooling efficiency.

Cylinder head (head) - The finned aluminum part on top of the engine

that is responsible for dissipating most of the engine’s heat. The
combustion chamber is machined into the bottom of the head.

Dyno - Abbreviation for dynamometer. A precise piece of testing

equipment that accurately measures engine power and torque
output over the engine’s entire RPM range.

EZ-Start - Traxxas on-board electric starting system. The system

consists of a hand-held starter control unit and an on-board gearbox
with an electric motor to spin the engine.

Filter foam - The oiled foam element inside the air filter housing. The

filter foam in the TRX 2.5 must be thoroughly cleaned and re-oiled
after every hour of run time.

Fit - Usually refers to the fit of the piston and sleeve. If the fit is tight,

the piston will feel very tight at the top of the sleeve (top dead
center), and the engine will have good sealing and compression.
If the fit is loose, compression will be low and both the piston and
sleeve should be replaced.

Flame-out - Occurs when the engine stops running at high RPM. Usually

the fault of an excessively lean fuel mixture or glow plug failure.

Fuel - (10%, 20%, 33%) The TRX 2.5 must have model engine fuel to

run. Traxxas Top Fuel

™

is recommended. Fuel is sold in quarts and
gallons from hobby dealers. The 10, 20, and 33% labeling refers to the
percentage of nitromethane contained in the fuel.

Fuel mixture - The ratio of fuel to air as determined by the needle

settings of the carburetor.

Fuel tubing (fuel line) - The thick silicone tubing that carries fuel from

the fuel tank to the carburetor.

Glow plug - The glow plug is located in the cylinder head at the top

of the combustion chamber. It contains an element that glows red
hot when voltage is applied. When the engine is being started,
the heat from the glow plug ignites the fuel mixture and starts the
combustion process.

Glow plug driver - This tool clips onto the glow plug and supplies the

required voltage to light the glow plug element. It is also called an
igniter. EZ-Start equipped engines do not require this separate tool.

THE TRX 2.5 RACING ENGINE

Header - The aluminum tube that connects the exhaust system to the

engine exhaust port. The length and diameter of the header must be
carefully selected to extract the most power from the engine.

High-speed needle (HSN) - Adjusts the carburetors fuel/air mixture at

high throttle openings.

Idle speed - The speed (RPM) the engine runs at when the transmitter’s

throttle trigger is at neutral.

Idle speed screw (ISS) - Located on the carburetor body. This screw

adjusts the idle RPM of the engine.

Lean - A running condition where the engine is not getting enough

fuel (for the available air). Symptoms include engine overheating,
or the engine runs for a short time and then stalls, particularly at
high speed. This is a dangerous condition that should be corrected
immediately or it can ruin your engine.

Leaning the mixture - Turning either the high-speed and/or low-

speed needle(s) clockwise to decrease the amount of fuel the engine
receives.

Low-speed needle (LSN) - Needle valve that controls the fuel mixture

at low throttle openings.

Needle valve - Valve consisting of a tapered needle that closes against

a corresponding seat to regulate fuel flow.

Nitro - Abbreviation for nitromethane, a component of model engine

fuel that improves fuel combustion and power output. Nitro also
refers to a class of R/C powered by model engines instead of electric.

Nitro content - The amount of nitromethane used in the fuel. Usually

measured as a percentage of the total fuel volume. Traxxas engines
are optimized to use 10-20% nitro. 33% nitro may be used for racing.

Nitromethane - Nitromethane is a component in the fuel that increases

power from the combustion process up to a point. Engines are
generally optimized to use a range of nitro content for the best
power.

O-ring - Rubber “O”-shaped ring used as a sealing gasket.

Pipe - Abbreviation for the tuned exhaust pipe on a nitro engine. See

“Tuned Pipe”.

Piston - The piston is the internal engine part that is attached to

the upper end of the connecting rod and moves up and down
in the cylinder sleeve. The precise fit between the piston and the
sleeve creates a seal that allows the engine to have the required
compression for combustion.

Port - Ports are openings in the sleeve that allow atomized fuel to enter

the combustion chamber and burned exhaust gases to exit. The
shape and location of the ports are a large factor in controlling the
engine timing and power output.

Priming - Manually causing fuel to move from the fuel tank up to the

carburetor. This is sometimes necessary after the engine has been
sitting for a long period of time and all of the fuel has drained back to
the tank. On a Traxxas model, this is done by holding your finger over
the exhaust tip for one or two seconds while the engine is starting.

Punch - A term that refers to how quickly the model responds to

throttle input or how quickly it accelerates.

Rich - A running condition where the engine is getting too much

fuel for the available air. It is better to run an engine slightly rich
to increase engine life. Excessively rich mixtures cause the engine
to have sluggish performance with exaggerated blue smoke and
unburned fuel coming from the exhaust.

RPM - Abbreviation for revolutions per minute (how many times the

engine crankshaft spins in a minute).

Sleeve - Internal engine part that contains the piston. The precise fit

between the sleeve and the piston creates a seal that allows the
engine to have the required compression for combustion. The sleeve
in a TRX engine is made of brass and is then hard-chrome plated.

Slide carburetor - The throttle on a slide carburetor closes and opens

by sliding a barrel in and out of the carburetor body. This type of
carburetor is preferred for performance use because it provides a less
restrictive “straight-through” air path than the barrel carburetor design.

Stall - When the engine stops running, usually due to an incorrect fuel

mixture setting or running out of fuel.

TDC - Top dead center. The top-most position of the engine

piston stroke.

pipe

Tuned

- The tuned exhaust pipe usually consists of a specially­shaped metal or composite chamber with baffles that is designed to
enhance the power output of the engine.

Wear-in - Fitment process that occurs during engine break-in where

internal engine parts develop an even more precise matched fit
through actual use under controlled circumstances.

WOT - Abbreviation for wide-open throttle.

T-MAXX • 17

THE TRX 2.5 RACING ENGINE

DANGER! Model engine fuel
is poisonous to humans
and animals. Drinking the
fuel can cause blindness
and death. Handle with
care and respect. Keep
fuel out of reach of small
children at all times! While
driving, do not leave your
fuel dispensing bottle on
the ground where a child
could have access to it.
Follow fuel label warnings.

18 • T-MAXX

The Fuel

Use the Right Fuel

It’s imperative that you use the correct fuel in your
TRX 2.5 Racing Engine for maximum performance
and engine life. Traxxas Top Fuel® should be used
to ensure correct engine lubrication, performance,
and ease of tuning. Traxxas Top Fuel has been
proven in thousands of engines, so you can count
on it every day for great performance.

•

Top Fuel is the only fuel which is 100% certified for use in Traxxas engines.

•

Traxxas Top Fuel is made with just the right balance of the highest
grade natural and synthetic lubricants to allow excellent throttle
response and the best top-end performance, without sacrificing
long-term durability.

•

All of the components in the fuel are carefully selected from the
best materials available and then custom blended to match the
metallurgy and temperature characteristics of Traxxas engines.

You may use 10, 20, or 33% nitro-content fuel. Try to use the same
percentage all the time, avoid switching back and forth between
fuels. We recommend that if you break in your engine on 20% fuel
that you stick with that percentage. If you do move to a higher
or lower percentage, make sure you readjust your fuel mixture to
compensate (see below).

Choosing a Nitro Percentage

A commonly asked question is “what is the difference between 10%,
20%, and 33% fuels?” Increasing the nitro in the fuel is almost like adding
extra oxygen to the combustion process. It burns more efficiently,
improves combustion, and delivers more power. When increased nitro
is used, more of the other fuel components are then required inside the
combustion chamber to maintain the perfect air/fuel ratio. Therefore,
overall fuel mixtures need to be richened slightly (on the high speed
needle, about 3/4 of a turn counterclockwise when changing from 20%
to 33%, about 1/2 of a turn counterclockwise when changing from 10%
to 20%). This allows greater fuel flow through the engine and promotes
cooler running, even at the maximum lean settings.

If 33% improves power, then it seems that the highest nitro content
available (beyond 33%) should always be used in the engine. In reality,
there are practical limitations. Engines are designed to run best within
a range of nitro percentages. How the engine is ported, the size of the
combustion chamber, and other factors determine how much nitro can

be efficiently used in the engine. The TRX 2.5 Racing Engine responds
exceptionally well to a maximum of 33% nitro, returning cooler temps,
more power, and a smoother throttle response. For those who want to
run higher nitro, 33% Top Fuel is the optimum nitro percentage for the
TRX 2.5 Racing Engine. Increasing the nitro beyond 33% can introduce
the need for engine modifications (ports, head shimming, etc.) to avoid
starting and tuning difficulties. There are limits to how much nitro an
engine can effectively use to make more power. Lower nitro percentages
have their own advantages. Nitro is an expensive component in the
fuel, so 10% nitro blend is more economical for the sport user. 10% also
provides greater latitude with the needle settings for easier tuning.

When using Traxxas Top Fuel, using higher nitro percentages does
not cause the engine to wear out faster. 33% Top Fuel contains the
same quality lubrication package as 10 and 20% Top Fuel. Some
non-Traxxas high-percentage nitro racing fuels do sacrifice some
lubrication in attempts to increase performance. We urge you to
not take chances with your engine investment and use Top Fuel for
consistent performance and long engine life.

What about Other Fuels?

Can other brands of fuel be used besides Top Fuel? There are other
fuels that can provide satisfactory performance; however, there could
be long-term costs in the form of decreased engine performance, loss
of tuning ease, and shorter engine life. Only use fuels that contain both
castor and synthetic oil.

Everyone has an opinion or a claim to make about fuel. The
engineering team at Traxxas has spent years developing TRX Racing
Engines. No one knows more about the specific fuel requirements of
Traxxas engines than Traxxas engineers. We strongly urge you not to
take chances with your engine investment and use the Traxxas fuel
made for the TRX 2.5 Racing Engine.

Handling the Fuel

•

Follow all directions and warnings on the fuel can.

•

Keep the fuel tightly capped at all times. Some components in the fuel
can evaporate very quickly and upset the balance of the fuel.

•

Do not store unused fuel in the fuel dispenser. Immediately return
fresh unused fuel back into the fuel can.

•

Do not mix old and new fuel. Never mix different fuel brands together.

•

Store the fuel in a cool dry location, away from any source of heat,
ignition, or combustion.

•

Read and follow the safety precautions on page 4 in this manual.

THE TRX 2.5 RACING ENGINE

Filling the Fuel Tank

Use the included fuel dispensing bottle to put fuel into
the T-Maxx’s fuel tank. To fill the fuel bottle, squeeze
the air out, insert the dispenser tip into the fuel can,
and release your grip on the bottle. As the bottle
expands, fuel will be drawn into it.

To fill your model, flip up the
spring-loaded cap on the fuel tank,
insert the tip of the fuel bottle, and
squeeze to dispense the fuel. Fill the
tank until the fuel level reaches the
base of the filler neck. Close the fuel
tank lid, making sure it closes tightly.

Fuel Tank Seal Adjustment

The rubber seal on the fuel tank is
important to the function of the engine. The fuel tank is pressurized
by the exhaust system to provide reliable fuel flow. If the tank lid
does not seal properly, an air leak will be created that can cause
your engine to run erratically and be difficult to start. If necessary,
the rubber O-ring tank seal can be adjusted for improved sealing by
tightening the screw on the underside of the tank lid.

The Air Filter

The TRX 2.5 Racing Engine air filter is specifically designed to deliver
maximum performance while protecting your engine from dust
and dirt. Use only the supplied filter. You will not improve engine
performance by switching to an aftermarket filter, and you may risk
engine damage due to poor filtration.

The TRX 2.5 Racing Engine air filter assembly consists of 3 pieces:

1. A rubber filter base

2. A plastic housing consisting of a permanently
assembled mesh cap and body

3.

An oiled foam element

You must clean the filter after every hour of run time, even if the filter
looks clean. This includes the break-in time. Clean your air filter after

break-in. Dust (which is often too fine to see) and dirt constantly move

through the filter anytime the engine is running. Even if you can’t see
dirt on the filter, it is present inside the foam after any amount of run

time. If you exceed the recommended cleaning intervals, your engine
will be damaged. Engine damage or wear due to dirt ingestion is easy
to detect, and one of the top causes of premature engine failure.

Air Filter Cleaning Instructions

1. Remove the air filter from the
carburetor bore by pulling the
entire filter assembly firmly to
the side to release it. Do not pull
straight up.

2. Disassemble the filter. Pull the
rubber air filter neck out of
the filter body. With the base
removed, the foam element is
visible in the bottom of the filter
body. Pull out the foam element.

3. Clean the filter parts by thoroughly washing all three pieces of the
filter assembly in hot soapy water (dishwashing detergent works
well). Repeat twice.

4. Thoroughly dry the parts with a clean towel or compressed air.
Remember to wear your safety glasses when working with
compressed air.

5.

Oil the foam element with foam filter oil. Use the supplied Traxxas

filter oil (part# 5263) or a high-quality, special-purpose foam filter oil,
such as that used for off-road motorcycle and ATV engines.This type
of filter oil is available at motorcycle pro-shops. Apply 30 drops of
the Traxxas filter oil evenly to the top, bottom, and sides of the filter
element (30 total drops divided among the 3 surfaces). Squeeze the
filter element repeatedly to help spread the oil throughout. The filter
element should be evenly colored by the oil. Even color indicates
that the oil is distributed evenly. Do not squeeze out excess oil.

Note: Do not use the air filter oil for anything other than the air
filter. It is

6. Reassemble the filter and install it on the engine, making sure
the rubber filter neck fits securely on the carburetor with no gaps
or air leaks.

not meant to be a lubricant.

11

T-MAXX • 19

THE TRX 2.5 RACING ENGINE

See page 27 for more
information on how air
density affects engine tuning.

A “turn” refers to
tightening (“turning in”) or
loosening (“turning out”)
mixture needles. A “full
turn” refers to turning the
needle 360°, so a “1/2 turn”
would be 180°, a “1/4 turn”
would be 90°, and so on.

Full Turn

Start

3/4 Turn

270°

1/2 Turn

20 • T-MAXX

360°

180°

1/8 Turn

45°

1/4 Turn

90°

The Carburetor

Understanding the Carburetor adjustments

The carburetor performs several functions. It controls the engine’s
speed by restricting the intake of air and fuel into the engine. It
atomizes the fuel (suspends the fuel droplets in the air) and also
controls the air/fuel ratio of the mixture entering the engine (how
much air for a given amount of fuel).

Air

Fuel

To help provide a better understanding of engine tuning and why
it’s necessary, the following is a brief explanation of the air/fuel
combustion process that takes place inside the engine.

In order to create the cylinder pressure that results in power, the
engine burns the air/fuel mixture. Both air and fuel, in correct
amounts, are needed for proper combustion. It is the carburetor’s
job to mix the air and fuel together (atomize the fuel), in the correct
proportion for the best possible combustion. This is the ideal air/fuel
ratio. The ideal air/fuel ratio required for the engine remains roughly
constant. Due to variations in atmospheric conditions (temperature,
humidity, altitude, etc.), fuel flow adjustment valves (called fuel
mixture needles) are required to meter the fuel and maintain the ideal
air/fuel ratio in these ever-changing conditions. For example, colder
air is more dense (more air molecules) for a given volume of air and
therefore requires more fuel (more fuel molecules) to maintain the

correct air/fuel ratio. Warmer air is less dense (fewer air molecules)
and therefore needs less fuel to maintain the correct air/fuel ratio. The
tuning needles are there to adjust how much fuel is made available for
the carburetor to mix with the available air (atomization).

Cold Air (More Dense)

(Warm Air) Less Dense

The Fuel Mixture Needles

The amount of fuel metered and atomized by the carburetor is
controlled by the two mixture needles, the high-speed needle and
the low-speed needle. The low-speed needle is used to meter the fuel
used by the engine at idle and low RPM (part-throttle) engine speed.
The high-speed needle is used to meter the fuel when the throttle is
open from part throttle to wide-open throttle (WOT). Two needles on
the TRX 2.5 Racing Engine provide precise control of the air/fuel ratio
across the engine’s entire RPM range.

The maximum possible fuel flow is always controlled by the high­speed needle. It works like the main water valve on a garden hose.
Turn it clockwise to close the valve, counterclockwise to open it.
When the throttle is at idle or partially open, the low-speed needle
meters the fuel flow at the outlet (needle seat) where the fuel enters
the carburetor venturi. This second valve acts like the spray nozzle
at the end of the garden hose in our example. When you accelerate
from idle, the throttle opens and the low-speed needle is pulled away
from the needle seat. This allows more fuel to flow with the increased
air flow. As the throttle is increased, the low-speed needle is pulled
completely away from the needle seat, leaving it fully open. At that

Water Valve

(Controls Overall Flow)

High Speed Needle

Richen

THE TRX 2.5 RACING ENGINE

•

Slightly lean fuel mixtures deliver stronger, more efficient
combustion and more power, but with less lubrication.

•

Slightly rich fuel mixtures deliver cooler running and more
lubrication but with slightly

less power.

See Tuning Your TRX 2.5
Racing Engine on page 26

for complete information on
adjusting the air/fuel mixture
and idle speed.

Water Nozzle

(Controls Fine Flow)

Low Speed Needle

point, fuel metering is entirely controlled by the high-speed needle.
Again, using our water hose example, when the spray nozzle at the
end of our garden hose is fully open, then the main water valve can
be used to adjust how fast the water flows.

The engine’s performance is directly linked to the fuel mixture.
Richening the fuel mixture increases the amount of fuel in the
air/fuel mixture ratio, and leaning the fuel mixture decreases the
amount of fuel in the air/fuel mixture ratio.

Lean

Rich

Tuning the engine means finding the perfect balance between the
two; excellent power to meet your needs while maintaining good
lubrication for long engine life. The optimal fuel mixture setting
is rich to provide a safety margin against having a lean condition if
some variable changes (such as the temperature from one day to
the next).

General fuel mixture

settings are measured by the number of turns
the needles are turned out from fully closed. The fuel mixture settings
have been pre-set from the factory to typical break-in settings. Do
not re-adjust your carburetor from the factory settings until after the
engine is started and running, and you have been able to observe the
engine running to assess what minor adjustments may be required
to compensate for fuel, temperature, and altitude. Adjustments are
usually made in 1/8 or 1/16-turn increments. If the engine sticks at top
dead center (TDC), see page 34 for instructions on freeing the engine.

The Idle Speed Adjustment

The idle speed adjustment screw controls the closed position of the
throttle slide. When the throttle servo is in its neutral position, the
throttle slide should be stopped against the idle speed adjustment
screw. Always use the idle speed adjustment screw to control engine
idle. See page 28 for instructions on adjusting the idle speed.

Factory Needle Settings

If your factory preset
carburetor adjustments have
been tampered with, use the
following settings:

• Set the high-speed needle to
4 turns out from closed.

• Set the low-speed needle so
the screw head (red in Fig. A)
is flush (even) with the end
of the slide (yellow in Fig. A).

Fig. A

Low-Speed

Needle Adjustment

Always use the factory
settings for initial starting.
Only use these settings when
the factory settings have
been lost.

Higher nitro requires a richer
fuel mixture. When running
33% fuel, richen your high­speed needle 3/4 turn if
previously running 20% nitro
and then re-tune the engine
for maximum performance.

T-MAXX • 21

THE TRX 2.5 RACING ENGINE

Using Other Chargers

Another convenient option
for charging the included
battery is an AC peak­detecting charger that plugs
directly into an AC wall
outlet, such as the EZ-Peak
Plus Charger with iD, Part
#2970. It contains special
peak-detection circuitry
that automatically shuts the
charger off when the battery
is fully charged.

Caution: Never use a
15-minute timed charger to
recharge your model’s battery
packs. Overcharging may
result, causing damage to the
battery packs.

THE TRAXXAS EZ-START ELECTRIC STARTING SYSTEM

The Traxxas EZ-Start brings the convenience of push-button electric
engine starting to your T-Maxx. The EZ-Start consists of a hand-held
control unit and an on-board motorized starter.

•

Power for the EZ-Start system comes from a 7.2-volt rechargeable battery
pack installed in the hand-held control unit.

•

The engine glow plug is heated automatically by the EZ-Start system,
eliminating the need to keep up with a separate glow plug igniter.

•

The voltage to the glow plug is kept constant, regardless of the
load placed on the starter by the starter motor.

•

The “Glow Plug” LED (light emitting diode) on the control unit
indicates the condition of the glow plug.

•

The “Motor” LED indicates the status of the EZ-Start electric starter motor.

•

The cush drive mechanism in the drive unit prevents damage to the
gears caused by engine kickback.

•

Smart Start™ protection circuitry prevents damage to the motor by cutting
power if the load on the motor or other electronics exceeds safe limits.

Charging the EZ-Start Battery

The included charger can be used to charge the included EZ-Start
battery pack. Do not charge batteries inside of an automobile. Read the

Safety Precautions section of this guide.

1. Plug the charger into a 12-volt

1

automotive auxiliary power socket.
The charger is compatible with 12-volt
automotive auxiliary power sockets only.
The LED on the charger will glow red to
indicate it is ready to charge a battery.

2. Connect the battery to begin charging.

2

Disconnected

Plug the battery into the charger.
The charger’s LED will flash green,
indicating that charging has begun.
The flashing green LED on the charger
indicates the charge progress.

3

Connected

3. Disconnect the battery when charging
is complete. When the battery is fully

charged, the LED will light solid green.

Charged

The battery will be warm in your hand.
Disconnect the battery.

CHARGER LED INDICATION MEANING

Solid Red LED Ready for Charging

Slowly Flashing Green LED Charging (see Charge Progress chart)

Solid Green LED Battery Fully Charged

Flashing Red LED Charger error

Installing the EZ-Start Battery

1. Press the tab in the end of the battery
compartment door to open (A).

2. Plug a fully charged 7.2-volt
battery pack into the
connector inside (B).

3. Twist the battery two or
three times to twirl the
battery plug wires. This
helps hold the wire and
battery in place when the
battery is installed in the
compartment (C).

4. Install the battery into the
compartment and press the
wires securely into place.

5. Snap the battery compartment door back on and lock the
end tab (D).

CHARGE PROGRESS

1 green flash 0 - 25% charged

x1

2 green flashes 25% - 50% charged

x2

3 green flashes 50% - 75% charged

x3

4 green flashes 75% or more charged

x4

Solid green LED 100% charged

D

A

B

C

22 • T-MAXX

2,7,12

Motor

Glow

Plug

Motor

Glow

Plug

Motor

Glow

Plug

Motor

Glow

Plug

Motor

Glow

Plug

Motor

Glow

Plug

Motor

Motor

Motor

Motor

Glow

Plug

Motor

Glow

Plug

Motor

Glow

Plug

THE TRX 2.5 RACING ENGINE

Using the EZ-Start

Your EZ-Start controller plugs into a 4-prong receptacle in the center of the
bed on your T-Maxx. When the red button on the controller is pressed, the
EZ-Start motor begins to spin the engine, and power from the control unit
heats the glow plug. Assuming all settings and preparations are correct,
the engine should start almost immediately.

Each of the two status indicator LEDs on the hand-

Motor

Motor

Motor

Glow

Glow

Glow

Plug

Plug

Plug

held control unit, the Motor LED and the Glow Plug
LED, should light green while starting. If either LED
fails to light while starting, there is a fault indicated
with that function.

Glow

Plug

Glow

Plug

Glow

If the Glow Plug LED fails to light, the glow plug may

Plug

be bad, or the glow plug wire may be damaged or
disconnected.

If the Motor LED fails to light and the starter fails to

Motor

Motor

Motor

Glow

Glow

Glow

Plug

Plug

Plug

operate, then the EZ-Start is in protection mode.

Protection Mode

The EZ-Start uses Smart Start

™

technology to monitor the condition
of the system and detect failures. The controller monitors the load
being placed on the EZ-Start motor. If the load becomes excessive,
the system shuts off power to the motor to prevent costly damage
to the motor and the controller. This may occur, for example, if the
engine floods with fuel during starting. The starter spins at first, but
when excessive fuel in the combustion chamber begins to lock up the
engine, the starter motor slows under the heavier load. This causes
the protection circuit to shut off the power to the motor. Allow at least
3 minutes for the starter motor to cool and the circuit to automatically
reset before continuing. Use the time to find and eliminate the
condition that caused the excessive load on the starter motor.

Use a Strong Starter Battery

A weak starter battery, or one that has not been fully charged, may
not deliver enough power to crank the engine over at the appropriate
RPM to keep the piston from sticking at top dead center (TDC). A new
engine will typically have a tight fit between the piston and the top of
the sleeve. This is a tapered fit, and a tight piston sleeve fit on initial
startup is desirable for those who want the best-performing engine.
Make sure you are using a good quality battery pack that is fully
charged (new batteries usually require several charge cycles to reach
peak voltage and full capacity). This is especially important with a new
engine that needs to be broken in. If the engine sticks at TDC, see
page 34 for instructions on freeing the engine.

Shutting Off The Engine

Turning off the switch for the radio will not
shut off the engine. To shut off the engine, use
the shut-off clamp on the fuel line. Squeeze
the clamp closed to shut off the fuel supply to
the engine. Don’t forget to release it when you
restart the engine.

Avoid shutting off the engine by placing your finger over the exhaust
outlet, especially if you are through driving for the day. This will
leave more unburned fuel in the engine that could lead to harmful
corrosion. Always be careful not to touch the exhaust pipe after

running, it can become very hot.

When the EZ-Start controller
is in protection mode, wait
at least three minutes before
attempting to start the engine
to give the starter motor time
to cool.

It’s normal for your EZ-Start
controller to become warm
after repeated use.

T-MAXX • 23

THE TRX 2.5 RACING ENGINE

See Important Points to
Remember on page 4 for other
precautions.

Never run your T-Maxx
indoors. Since the TRX 2.5
Racing Engine exhaust fumes
are harmful, always run your
model outdoors, in a well­ventilated area.

Your TRX 2.5 Racing Engine
doesn’t usually require priming.
If you do need to prime your
engine, watch the fuel line
carefully to avoid flooding
your engine. See page 34 for
information on clearing a
flooded engine.

Factory Needle Settings:

Your carburetor is preset at
the factory to give the correct
air-to-fuel ratio and idle speed
for engine break-in. Do not
adjust the carburetor unless
you observe a poor running
condition that requires
correction (see page 21 for
stock settings).

Higher nitro requires a richer
fuel mixture. When running
33% fuel, richen your high­speed needle 3/4 turn if
previously running 20% nitro
and then re-tune the engine
for maximum performance. See
page 18 for more information.

24 • T-MAXX

13,14

BREAKING IN YOUR TRX 2.5 RACING ENGINE

The TRX 2.5 Racing Engine uses a ringless, aluminum-brass-chrome (ABC)
piston/sleeve construction. This type of engine design relies on a very precise
running fit between the piston and sleeve for cylinder sealing. Engine break-

in is necessary to allow the piston and sleeve to develop an extremely
precise fit and optimum cylinder sealing. Therefore, proper engine break­in is critical to achieving the fastest, most reliable engine performance.

Allow yourself about 1 to 1½ hours to complete the break-in procedure.
The engine break-in period will take 5 tanks of fuel in a T-Maxx. The break­in time is not the time to impress your friends with your new T-Maxx. You

must wait until the engine is fully broken in before attempting sustained
high-speed running. Patience and careful attention during break-in will

reward you with the best-performing TRX 2.5 Racing Engine possible.

During break-in, your engine may appear to malfunction with symptoms
like stalling, inconsistent performance, and fouled glow plugs. These are
simply the normal “break-in pains” engines sometimes go through. They
will disappear once your engine is fully broken in. Many owners report
not experiencing any of these symptoms with TRX Racing Engines. We

recommend replacing the glow plug with a new one (included) after
the engine break in procedure. Use the supplied glow plug wrench to

remove the glow plug from the engine’s cylinder head (see page 15).

Engine Break-in Procedure

The focus during break-in is to vary and limit the engine speed. This will
be accomplished by accelerating and stopping at different rates for the
first 5 tanks of fuel. As the engine begins to break-in, the duration and
intensity of the acceleration will gradually increase. Sustained high-
speed running is not permitted until the 6th tank of fuel. Perform the
initial break-in on a large, flat, paved surface. T-Maxx is very fast and

by tanks 4 and 5 you will need plenty of room for the truck to run in.
Apply all throttle and braking actions gently. Abrupt acceleration or
braking could cause the engine to stall unnecessarily.

•

Special break-in fuels are not recommended. Use the same fuel you
plan to use everyday.

• I

f possible, avoid breaking-in the engine on extremely hot or cold

days (see page 26).

•

Pay careful attention to the fuel level. Do not allow the fuel tank to
run completely empty. An extremely low fuel level causes the mixture
to run too lean. This could result in a burned glow plug or extremely
high engine temperatures.

•

Do not attempt to break in the TRX 2.5 Racing Engine by idling it
on a stand. This will produce poor results.

•

Keep extra Traxxas glow plugs handy. The break-in process can cause
deposits to form on the plug, leading to plug failure.

•

Change or clean your air filter after break-in.

•

Follow the instructions exactly for each of the first 5 tanks of fuel.

Starting Your TRX 2.5 Racing Engine for the First Time

Before you start your TRX 2.5 Racing Engine for the first time, make sure
you have read all instructions and precautions in this manual. Pay close

attention to the tank-by-tank break-in instructions in the next section,
and make sure you have read and understood them before you run
your engine.

Your engine must be at room temperature (70°F or 21° C) or above the
first time you start it. If it’s cooler than room temperature outside, remove

all fuel and keep your T-Maxx indoors until you’re ready to start it and
then take it outside. If it’s colder than 45°F, special considerations should
be made. See cold weather break-in on page 26. We do not recommend
running the model in temperatures below 35°F.

1. Turn on the radio system (see page 11).

2. Make sure the throttle trigger on the
transmitter is in the idle (neutral) position.

3. Connect the EZ-Start controller according to
the instructions on page 22.

4. Press the starter button in short two-second
bursts and watch for fuel moving through
the fuel line up to the carburetor. Watch
closely! The fuel moves very fast. If the fuel
doesn’t move through the line within 5 seconds, prime the engine
by briefly (one or two seconds) covering the exhaust outlet with your
finger and pressing the EZ-Start button until the fuel is just visible in
the carburetor fuel line. Watch carefully! If the engine is primed too

long, it will flood with fuel and stop turning.

5. Once fuel reaches the carburetor, the engine should
quickly start and idle.

6. Disconnect the EZ-Start controller from the model.

7. Proceed with the engine break-in.

8. Do not rev your engine with no load (wheels off the ground).

If your engine doesn’t start, refer to the troubleshooting tips on page 35 or
go online to www.traxxas.com/support. If your factory fuel mixture settings
have been altered, refer to page 21. If you still have problems, contact
Traxxas Customer Support at 1-888-TRAXXAS or [e-mail].

THE TRX 2.5 RACING ENGINE

Tank 1

1. Drive the model with the body off.

2. Driving procedure: Gently pull the throttle trigger to 1/4 throttle
over a 2-second count. Then gently apply the brake to stop.
Count the two seconds out while accelerating: one thousand one,
one thousand two, and then stop. Operate the throttle trigger as
smoothly as you can. Repeat this starting and stopping procedure

until the first tank of fuel is nearly empty.

3. Look for thick blue smoke exiting the exhaust outlet. If there is
no smoke, richen the high-speed needle 1/4 turn, by turning the
needle counterclockwise.

4. When the fuel tank is nearly empty, shut off the engine by pinching
the fuel line connected to the carburetor (use the installed clamp).

5. Let the engine cool for 15 minutes.

Note: If at any point the engine cuts out or stalls during gentle
acceleration, richen the high-speed needle 1/4 turn by turning the
needle counterclockwise.

Tank 2

1. From tank 2 forward, T-Maxx should be driven with the body on.

2. Driving procedure: Gently pull the throttle trigger to 1/2 throttle
over a 2-second count. Then gently apply the brake to stop. Count
the two seconds out while accelerating: one thousand one, one
thousand two, and then stop. Repeat this starting and stopping

procedure until the second tank of fuel is nearly empty.

3. When the fuel tank is nearly empty, shut off the engine and let it cool
for 15 minutes.

Tank 3

1. Driving procedure: Gently pull the throttle trigger to 1/2 throttle
over a 3-second count. Then gently apply the brake to stop. Count

the three seconds out while accelerating: one thousand one, one
thousand two, one thousand three, and then stop. Repeat this

starting and stopping procedure until the third tank of fuel is
nearly empty.

2. As the engine loosens, the idle speed may increase and cause
the model to try to creep forward when stopped. Reduce the
idle speed by turning the idle adjustment screw (see page 15) on the
carburetor counterclockwise.

. When the fuel tank is nearly empty, shut off the engine and refuel.

3

From here on, you do not need to let the engine cool between tanks.

Tank 4

1. Driving procedure: Gently pull the throttle trigger to full throttle
over a 3-second count. Then gently apply the brake to stop. Count

the three seconds out while accelerating: one thousand one, one
thousand two, one thousand three, and then stop. Repeat this

starting and stopping procedure until the fourth tank of fuel is
nearly empty.

2. Apply the throttle gradually! Your finger should not reach full throttle
until the end of the three-second count. T-Maxx may try to shift into
second gear. If it does, reduce the throttle input. Do not let T-Maxx
shift out of first gear.

3. Keep your driving smooth and consistent.

4. When the fuel tank is nearly empty, shut off the engine and refuel.

Tank 5

1. Driving procedure: Gently pull the throttle trigger to full throttle
over a 3-second count, hold for 2 more seconds, and then
gently apply the brake to stop. Count the five seconds out while
accelerating. Repeat this starting and stopping procedure until the
fifth tank of fuel is nearly empty.

The model should now be shifting into second gear. If it is not, try

2.
turning the high-speed needle clockwise 1/8 turn to lean the fuel
mixture slightly and test for shifting.

3. When the fuel tank is nearly empty, shut off the engine and refuel.

Tank 6
STOP! Clean your air filter before you proceed. Refer to the instructions

on page 19. During the sixth tank of fuel, the engine can be tuned for
general performance use. Proceed to Tuning your TRX 2.5 Racing Engine.

High Altitude Operation:
If you live in a high
altitude region (5000 or more
feet above sea level), the
lower air density may require
you to lean your high-speed
fuel mixture slightly from the
factory break in settings. Try
this if you are experiencing
difficult starting or extremely
sluggish engine performance
at high altitude.

As you gain experience in
the hobby, you may discover
that many people have
differing opinions on what
is the proper procedure to
break-in a model engine.

Only use the Traxxas break-in
procedure. Other break-in
procedures could result in a
weak, damaged, or otherwise
poor performing engine.

The procedure outlined
here was extensively tested
and proven to yield better
performing engines than
other “common” break-in
methods. Even if you have
years of experience using
model engines, please do not
ignore this caution!

TANK THROTTLE TIME COOL BODY NOTES

1 1/4 2 seconds 15 minutes Off Apply throttle gradually.

2 1/2 2 seconds 15 minutes On Apply throttle gradually.

3 1/2 3 seconds - On Reduce idle speed if necessary.

4 Full 3 seconds - On Do not allow shifting to high gear.

5 Full 5 seconds - On Accelerate over 3 second count, hold for 2 seconds.

T-MAXX • 25

THE TRX 2.5 RACING ENGINE

When tuning for
performance, watch closely
to notice when there is no
longer any increase in speed
or power when the
high-speed mixture is lean.
If you lean the high-speed
mixture to the point that the
engine cuts-out, hesitates,
or stalls, you are well into
the danger zone and engine
damage is likely. Richen the
high-speed needle 1/4 turn
and retune.

For your convenience, the
low-speed needle has a
positive stop that prevents
it from being over tightened
and damaging the needle
and seat. This also provides
an easy way to gauge how
many turns out from closed
the low-speed needle
adjustment is set to.

26 • T-MAXX

15

Winter Break-in Tips

During the break-in process, the piston and sleeve wear into
each other to form a precise fit. The engine needs to heat up to a
temperature around 200 to 215°F to allow the piston and sleeve to
achieve this fit properly. A precise fit between these two components
is critical for proper compression and optimum performance. If the
engine runs too cold during break-in, the piston and sleeve will not
expand to their appropriate sizes for break-in, and this can lead to
premature wear of these components. This wear may not become
apparent until after winter has past, and the engine is operated under
warmer running conditions.

•

Warm the engine to approximately room temperature by removing
all fuel and storing the vehicle inside at room temperature until just
before starting the

engine. An extremely cold engine can become

difficult to start.

•

After the engine is running, it is important to keep the temperature
of the engine up around 200 to 215°F during break-in. In weather
below 45°F, the TRX 2.5 Racing Engine will tend to run at lower
temperatures between 160 to 180°F (when tuned at proper break-in
mixture settings). This is too cool for break-in. Do not lean the fuel
mixture to increase engine temperature! This will also decrease
lubrication and cause your piston/sleeve to wear prematurely.

•

Wrap the cooling head with a paper towel,
clean rag, or sock to help keep the engine
running around the recommended 200
to 215°F break-in temp. If too much heat
is contained, the engine can actually run
too hot. Make sure that you monitor the
engine’s temp closely for the first couple
of tanks until you get the right amount of cover for the cooling head.
This will, of course, depend on your current weather conditions.
Adjusting the cover up and down, exposing more or fewer cooling
fins, is a convenient way to regulate engine temps.

•

For owners that do not have access to a temperature probe, a drop
of water on the cooling head (around the glow plug area) can be
used to estimate the engine’s temperature. The drop of water should
slowly sizzle for approximately 6 to 8 seconds if the engine is around
200 to 210°F. If the water sizzles for only a few seconds, then it is likely
that it is over 220°F, and needs to cool down. If the water takes a long
time or does not evaporate at all, then the engine is too cool.

•

We do not recommend that you operate your engine below 35°F. If
you insist on running your vehicle below 35°F, be aware that nitro
engines may be very difficult to start and tune at extremely cold
temperatures. Also, at temperatures below freezing, nitro fuel can
actually begin to gel up, and this can be harmful to the engine.

Follow the remaining break-in procedures as outlined in this Owner’s
Manual. This, along with the steps listed above, will ensure a good break­in for your new nitro engine, and provide many hours of enjoyment.

TUNING YOUR TRX 2.5 RACING ENGINE

The engine’s performance
depends on the fuel
mixture. Turn the mixture
needles clockwise to
lean the fuel mixture and
counterclockwise to richen
it. Leaning the fuel mixture
will increase engine
power up to the engine’s
mechanical limits. Never

run the engine too lean
(not enough fuel flow).
Never lean the engine so
far that it begins to cut­out or stall. Leaning the

engine beyond the safe
allowable limits will result
in poor performance and
almost certain engine
damage. Indications of an

overly lean mixture include:

•

Cutting out or sudden loss of power during acceleration.

•

Overheating (temperature beyond 270° F at the glow plug).

•

Little or no blue smoke coming from the exhaust.

If any of these conditions are present, stop immediately and richen
the high-speed mixture 1/4 turn. The engine will probably be slightly
rich at that setting and you can then retune for performance. Always
tune for performance by starting rich and moving leaner toward the
ideal setting. Never try to tune from the lean side. There should always
be a light stream of blue smoke coming from the exhaust.

THE TRX 2.5 RACING ENGINE

Before you begin tuning, the engine should be warmed up to its normal
operating temperature and running slightly rich. All final tuning adjustments
must be made to the engine at its normal operating temperature. You can
tell the engine is running rich by noting any of the following:

•

Sluggish acceleration with blue smoke coming from the exhaust.

•

T-Maxx may not shift into second gear.

•

There is unburned fuel spraying from the exhaust tip.

•

Leaning the high-speed fuel mixture increases performance.

High-Speed Fuel Mixture Adjustment

With the engine warm and running at a rich setting, gradually lean the
high-speed fuel mixture in 1/16 turn increments. Make several high­speed passes after each adjustment to clear out the engine and note any
change in performance. The TRX 2.5 is extremely powerful. Remember
to apply the throttle gradually to prevent wheelies or loss of control.
Continue this procedure until there is no longer any performance
improvement. If any one of the following conditions occurs, the fuel

mixture is already past the maximum safe lean setting:

1.

There is no longer any performance improvement.

2.

The engine begins to cut out at high speed (Danger!).

3.

There is a sudden loss of power during acceleration (Danger!).

4.

The engine begins to overheat. Symptoms of overheating include:

•

Steam or smoke coming from the engine (not exhaust)

•

Hesitation or stalling during acceleration

•

Popping or clattering sound when decelerating (detonation)

•

Fluctuating idle speed

•

Temperature measurement above 270°F at the glow plug

(A temperature reading above 270°F alone does not necessarily

indicate overheating. Look for other symptoms of overheating
combined with temperature for a more accurate warning)

Richen the fuel mixture to the optimum setting by richening the
high-speed needle at least 1/8 turn counterclockwise and retest. This
setting will extend engine component life.

Low-Speed Fuel Mixture Adjustment

The low-speed mixture is always set after the high-speed needle is
correctly adjusted. The low-speed mixture is set using the “pinch test”:

1.

Once the engine is warm, do several high-speed runs to confirm
that the high-speed needle is set correctly.

Bring the vehicle in and pinch closed the fuel line going into the

2.
carburetor (use the engine shut-off clamp). The engine should run for
2-3 seconds, speed up, and then shut off.

3. If the engine runs longer than 3 seconds, then lean the low-speed
needle 1/16 turn, make several more high-speed runs, and retest.

4. If the engine shuts off immediately without speeding up, then richen
the low-speed needle 1/8 turn, make several more high-speed runs,
and retest.

When the low-speed

needle is set correctly, the engine’s throttle response
should be very quick, even to the point of making it difficult to keep
T-Maxx from doing a wheelie when you accelerate!

Fuel Mixture Adjustment Chart

If the... is..

Humidity Lower

Higher

Pressure
(barometer)

Temperature

Altitude

Nitro %

Lower Less dense Leaner

Higher More dense Richer

Lower More dense Richer

Higher Less dense Leaner

Lower More dense Richer

Higher Less dense Leaner

Lower - Leaner

Higher - Richer

then the air
density is...

Slightly
more dense

Slightly
less dense

adjust (correct) the
fuel mixture to be...

Slightly richer

Slightly leaner

When adjusting the low­speed fuel mixture, it is very
important to make several
high-speed runs with T-Maxx
between adjustments to
clear out any excess fuel.
Perform the pinch test
immediately after. If the
engine is allowed to idle
for a long period of time, it
could “load up” with fuel
and give you an inaccurate
measurement from your
pinch test.

Higher nitro requires a
richer fuel mixture. When
running 33% fuel, richen
your high-speed needle 3/4
turn if previously running
20% nitro and then re-tune
the engine for maximum
performance. See page 18
for more information.

T-MAXX • 27

THE TRX 2.5 RACING ENGINE

28 • T-MAXX

Idle Speed Adjustment

Once the high- and low-speed mixtures have been set, reduce the idle
speed to the minimum reliable idle speed. Remember, this adjustment
should be made while the engine is running at normal operating
temperature. Always use the idle speed adjustment screw to control
engine idle.

1. When the throttle servo is in its neutral position, the throttle slide
should be stopped against the idle speed adjustment screw.

2. Turn the screw counterclockwise to reduce the idle speed or clockwise
to increase it. The idle speed should be set as low as possible while still
maintaining reliable running characteristics.

Fine-Tuning the Carburetor

After fine-tuning your TRX 2.5 Racing Engine at the end of the break­in procedure, no major adjustments to the fuel mixture are usually
necessary. Make note of the temperature, humidity, and barometric
pressure at the time you finished fine tuning your carburetor. Current
weather conditions can be found online from national websites, local TV
news websites, and television. This information will be considered your
baseline setting.

You may need to adjust your carburetor needles to compensate for
changes in temperature and barometric pressure (air density) from day to
day. Generally, you’ll need to richen the fuel mixture when the weather is
colder than your baseline temperature and the air density is higher. Lean
the fuel mixture when weather is warmer than your baseline temperature
and the air density is lower. The chart below provides general guidelines
on how weather conditions affect air density when they move higher or
lower than your baseline setting (see page 20 for detailed info on how air
density affects mixture settings).

Tuning the Engine by Temperature

The following procedures require an optional infrared temperature probe
or on-board temperature gauge. Engine temperature can be used as
an effective tuning aid when you understand the relationship between
engine temperature and ambient temperature. The engine operating
temperature, when tuned for maximum performance, will vary according
to atmospheric conditions, engine load, gauge accuracy, and many other
factors. The atmospheric condition that has the most influence on engine
temperature is air temperature. Expect the engine temperature to vary
almost in direct proportion to air temperature. Assuming you tuned
the engine for the same maximum performance each day, the engine
will run about twenty degrees hotter when it’s ninety degrees outside

than it would in seventy-degree weather. For this reason, we cannot
give you a definitive temperature range that indicates the best possible
engine tuning.

There is NO optimal temperature that can be used as a target to deliver
the best engine tuning. Do not rely on a temp gauge alone to tune
your engine. Tune the engine by paying very close attention to how
it responds to changes in fuel mixture (more smoke/less smoke, fast/
sluggish, reliable/stalling, smooth sound/ muffled sound, etc).

Once the engine is tuned, then observe the temperature.

The temperature gauge

can aid you in tuning by giving you a relative
indication of how your adjustments are affecting the engine and to help
prevent you from reaching excessive engine temperatures. For example,
as you lean the fuel mixture, the engine performance will increase along
with the temperature. If you continue to lean the fuel mixture and the
temperature increases but the engine performance does not change,
then you have exceeded the maximum safe lean setting. Make note of the
engine temperature. Generally, try to keep your engine from exceeding
270°F when measured at the glow plug. If necessary, increase airflow
to the engine by cutting out the rear of the body, windshield, and front
valance. In some situations, the engine may perform very well with no
stalling, lagging, or hesitation at temperatures above 270°F, particularly in
very hot climates.

If richening the fuel mixture to bring the temperature down to 270°F
results in poor,

sluggish performance (engine never cleans out) then return
the engine back to a satisfactory state of tune based on how it sounds and
performs (always with a visible stream of blue smoke coming from the
exhaust) . If engine temperature is exceeding 270°F with proper cooling
and no signs of abnormal running, then avoid running the engine at its
maximum lean setting. Watch closely for any signs of overheating.
Richen the fuel mixture slightly to provide a safety margin of additional
cooling lubrication.

•

Steam or smoke coming from the engine (not exhaust)

•

Hesitation or stalling during acceleration

•

Popping or clattering sound when decelerating (detonation)

•

Fluctuating idle speed

Symptoms of overheating include:

DRIVING YOUR T-MAXX

INTRODUCTION

Your TRX 2.5 Racing Engine is broken in, the fuel mixture is balanced,
and the idle is set…now it’s time to have some fun! This section
contains instructions on making adjustments to your T-Maxx. Before
you go on, here are some important precautions to keep in mind.

•

Don’t run your T-Maxx in water, mud, snow, or wet grass. It’s
tempting, but water and mud are easily drawn through the air filter
and will severely damage the engine. Small amounts of moisture
can cause electronics to fail and loss of control over your T-Maxx.
Snow is frozen water. Do not drive the T-Maxx in snow or the
electronics could be damaged by water.

•

The TRX 2.5 Racing Engine is extremely powerful. Remember to
apply the throttle gradually to prevent loss of control. T-Maxx is
very fast and responsive and is intended for experienced drivers.
Do not drive over the limits of your reflexes and ability. Drive with
caution at all times and gradually build up your ability to maintain
control at T-Maxx’s upper performance limits.

•

Don’t hold T-Maxx off the ground and rev the engine excessively
with no load on the engine. This practice could result in internal
engine damage. Avoid over-revving the engine when T-Maxx is
airborne after a jump.

•

Avoid excessive high-speed running for extended periods of time
or over long distances. This could cause the engine to build up
enough speed to exceed maximum safe RPM limits.

•

Don’t drive your T-Maxx with drivetrain damage of any kind. The
engine could be damaged due to overloads caused by drivetrain
friction, or over-revving caused by loose or missing parts.

•

Don’t tow anything with your T-Maxx. The engine is cooled by airflow
created by speed. Towing creates a high load on the engine, and at
the same time limits cooling of the engine due to low vehicle speed.

•

If your T-Maxx gets stuck, stop driving immediately. Move the
vehicle and then continue driving.

•

Never turn off the radio system while the engine is running. The
truck could run out of control.

Forward and Reverse Operation

Forward and reverse gears are selected
with the shift button located in the
transmitter handle grip. The switch
is normally in the down, or forward,
position.

•

To shift into reverse, bring your
T-Maxx to a complete stop and push
the shift button up. Accelerate to
engage the gear.

•

To return to forward gear, repeat the
same procedure but move the shift button down.

•

T-Maxx will not shift between forward and reverse unless the truck
is stopped. If it will not shift, then refer to the troubleshooting
section on www.Traxxas.com or call Traxxas support.

Shift Reverse

Shift Forward

Driving Tips

•

Monster trucks by design have a high center of gravity that
requires a different driving technique. To prevent rollovers, slow
down as you approach turns and then apply moderate throttle
through the turns. This technique will help T-Maxx grab the surface
and turn sharper.

•

Do not apply brakes and turn the wheel at the same time. You
could tip the truck over.

•

When jumping, apply some throttle while T-Maxx is in the air to
keep the truck’s nose up and land level on all 4 wheels. Be careful
not to over-rev the engine or land at full throttle. Either could
seriously damage your T-Maxx. If the nose of the truck is too high,
then quickly tap the brake to level the truck in the air.

•

Drive over large obstacles (such as curbs and rocks) at an angle,
instead of head on. This will allow the suspension to articulate and
absorb the impact much easier.

•

Even though T-Maxx is capable of high speed in reverse, it is very
difficult to control while driving in reverse. Limit your reverse
speed to prevent crashing or flipping your T-Maxx.

•

Change or clean your air filter element after each hour of running.
This is critical for the life of your engine. Running time includes the
engine break-in period.

16

T-MAXX • 29

0°0°

1°

1°

30 • T-MAXX

TUNING ADJUSTMENTS

Adjusting the Slipper Clutch

The T-Maxx features an adjustable slipper clutch on the spur gear to
help protect the drive train from sudden shock loads (such as landing off
of jumps with the engine at full throttle). Under normal conditions the
slipper clutch should not slip. Before adjusting the slipper clutch, turn the
model off. Do not adjust the slipper clutch while the engine is running.

Use the supplied glow plug (universal) wrench to tighten the slipper nut
(clockwise) until it stops, and then back the nut out 1/4 of a turn. If you
notice any decrease in performance after making changes to the slipper
clutch adjustment, then it may be too loose. The slipper must not be
allowed to slip during normal acceleration or the slipper could be damaged.

Adjusting the Two-Speed Transmission

The T-Maxx comes equipped with a two-speed transmission. When the
shift point on the transmission is adjusted correctly, it will maximize
acceleration and improve drivability. If necessary, use the supplied

2.0mm hex wrench to adjust the shift point.

1. Stop the engine.

2. Remove the large rubber plug from the transmission housing.

3. Look into the hole in the transmission housing and rotate the spur
gear until the access hole in the aluminum drum is visible.

4. Once the access hole is
visible, hold the spur gear
and use your finger to turn
the primary gear shaft,
which extends from the
transmission housing. Turn
it clockwise. Note that you
will see two set screws pass
under the access hole. As
you slowly turn the primary
gear shaft counterclockwise, the first set
screw that becomes visible holds the
two-speed mechanism on to the shaft.
Do not loosen this screw. The second
set screw is the adjustment screw.

5. Insert the 2.0 hex wrench through the
clutch drum and into the adjustment
set screw.

Primary Gear Shaft

6. Turn the adjustment screw 1/8 turn clockwise to raise the shift
point (later shifts). Be careful not to over tighten the adjustment
screw or you may damage the tension spring. Do not make
constant adjustments or you will loosen the screw’s locking device.

7. Turn the adjustment screw 1/8 turn counterclockwise to lower the
shift point (earlier shifts). Be careful not to loosen the adjustment
screw too much or you may cause the screw and spring to fall out
(requiring major disassembly and repair).

8. Use 1/8-turn increments to find the approximate desired
shift point.

9.

Check performance by running a test lap after each adjustment.

10. Use 1/16-turn increments to fine-tune the shift point.

11. Be sure to reinstall the access plug to prevent dirt from entering
the transmission.

Adjusting the Toe-in

Your T-Maxx comes from the factory with zero degrees of toe-in in the
front, and one degree of toe-in in the rear. You can adjust the toe-in on
the front and rear of the truck. Set the steering trim on your transmitter
to neutral. Now, adjust your steering turnbuckles so that both front
wheels are pointing straight ahead and are parallel to each other (0
degrees toe-in). This
will ensure the same
amount of steering in
both directions. Adjust
the rear toe control links
so that the rear wheels
have 1˚ of toe-in.

TUNING ADJUSTMENTS

0°0°

1°

1°

Adjusting the Camber

Two pivot balls are accessible through
the spokes of each of the wheels on your
T-Maxx. From the factory, the pivot balls are
completely tightened into the suspension
arms, which give each of the wheels –1˚ of
camber. Unscrewing the bottom camber
pivot ball with a 2.5mm hex wrench will
increase the wheel’s negative camber. You should not adjust the top
pivot ball; unscrewing it will increase positive camber and will also
change the wheel’s toe-in.

-1°

-1°

Fine Tuning the Shocks

The eight shocks (oil dampers) on your
T-Maxx have tremendous influence
on its handling. Whenever you rebuild
your shocks or make any changes to
the pistons, springs, or oil, always do it
carefully and in sets (front or rear). Piston
head selection depends on the range of
oil viscosities that you have available. For
example, using a two-hole piston with
lightweight oil will give you the same
damping as a three-hole piston with
heavier oil. We recommend using two-hole
pistons with a range of oil viscosities from
10W to 40W (available from your hobby
shop). The thinner viscosity oils (30W or
less) flow with less resistance and provide
less damping, while thicker oils provide
more dampening. Use only 100% pure silicone shock oil to prolong
seal life. From the factory, the T-Maxx uses 30W oil.

The ride height for the T-Maxx can be adjusted by adding or removing
the clip-on spring pre-load spacers. Note that changes in ride height
will occur when changes in shock angle or spring rates are made. You
can compensate for ride height changes by changing the pre-load
spacers on the shocks.

Adjusting the Suspension

The T-Maxx has adjustable suspension so that it may be optimized for
different kinds of terrain and driving styles.

Caster Adjustment

The T-Maxx offers the ability to adjust the caster angle of the front
suspension. Caster adjustment may be used to influence the understeer/
oversteer handling characteristics of the T-Maxx. Increasing the caster
angle will increase the tendency of the truck to oversteer (less traction
on the rear tires, more traction on the front tires), while decreasing the
caster angle will cause the truck to have a tendency to understeer (push
in the turns). This effect becomes more pronounced at higher steering
angles and higher spring rates. Caster is adjusted by repositioning the
shims on the pivot point of the upper suspension arms.

The stock caster setting is 7 degrees, with one shim at each end of the
arm. Reduce the caster angle to 4 degrees by removing the rear shim
and inserting it next to the front shim. The caster angle can be increased
to 10-degrees by removing the front shim and inserting it next to the
rear shim.

Factory toe-in settings can
be achieved by installing the
rod ends on the turnbuckles
until they bottom out
against the shoulder. If you
desire more toe-out, the
tips of the rod ends must be
trimmed to allow them to
screw down further onto the
turnbuckle threads.

A camber gauge (available
at your local hobby shop)
can be a useful tool for
alignment setting.

T-MAXX • 31

0

TUNING ADJUSTMENTS

For easier access to the
rear-most shock mounting
screw, remove the one end
of the rear turnbuckle. In the
front, remove the suspension
pin from the lower front
suspension arm to gain easier
access to the lower shock
mounting screws.

Shock Mounting Positions

Big bumps and rough terrain require a softer
suspension with the maximum possible
suspension travel and ride height. Racing on
a prepared track or on-road use requires a
lower ride height and firmer, more progressive
suspension settings. The more progressive
suspension settings help reduce body roll
(increased roll stiffness), dive during braking, and
squat during acceleration.

The innermost upper shock mounting position
(0) on the shock tower is intended for use with
the first generation T-Maxx suspension arms.
With the second generation arms (2.5-powered T-Maxx), position (0) can be
used for tuning with the inner pair of lower shock mounting positions on the
arm (1,2). It is not compatible with lower shock mounting positions 3 and 4
on the second generation (2.5-powered T-Maxx) arms. Upper shock mounting
position (A) should generally be used with lower shock mounting positions
1 and 2. Generally, upper shock mounting position (B) should be used with
lower shock mounting positions 3 and 4. Other combinations may be used to
achieve individualized suspension settings.

Lower Shock Mounting Positions

In the out-of-the-box configuration, the shocks are installed in position (A) on
the shock tower and position (2) on the lower suspension arm. This setting
allows for moderate suspension travel and ride height. The more vertical
position of the shocks allows for lower shock progression and the soft, plush
feel that’s characteristic of the T-Maxx.

2.5

2

1.5

Lower Mount 1, Upper Mount 0
Lower Mount 2, Upper Mount 0
Lower Mount 1, Upper Mount A
Lower Mount 2, Upper Mount A
Lower Mount 3, Upper Mount A
Lower Mount 4, Upper Mount A
Lower Mount 1, Upper Mount B
Lower Mount 2, Upper Mount B
Lower Mount 3, Upper Mount B
Lower Mount 4, Upper Mount B

Wheel Force vs. Wheel Travel

The outer pair of holes on the lower suspension arm should be used to lower
the ride height of the T-Maxx and increase the spring force (at the wheel).
This setting will improve high-speed cornering on smoother terrain by
lowering the center of gravity and providing a firmer suspension feel. Body
roll, brake dive, and squat will be reduced.

Spring rate (at the wheel) increases as the lower shock mounting position
is moved from position (1) to position (4). This is equivalent to using stiffer
springs. Use higher spring rate settings for flatter terrain with smaller and
fewer bumps and lower spring rate settings for bigger bumps.

Ride height decreases as the lower shock mounting position is moved from
position (1) to position (4). Each pair of lower shock mounting holes (1,2 and
3,4) has equal ride height. Use lower ride height for high-speed cornering
and flat terrain, and when racing on relatively smooth tracks. Increase the
ride height for rougher terrain and tracks.

Upper Shock Mounting Positions

The upper shock mounting positions will have the opposite affect on the
suspension that the lower shock mounting positions.

Spring rate (at the wheel) increases as the upper shock
mounting position is moved from position (A) to position (B).

Ride

mounting position.

Use the chart
The horizontal length of the lines indicates the amount of suspension travel.
The angle or slope of the lines indicates the spring rate (at the wheel).

More Firm

is not affected by changes in the upper shock

height

below to see the effect of the various shock mounting positions.

Lower Mount 4

Lower Mount 3

Lower Mount 2

Lower Mount 1

32 • T-MAXX

1

Wheel Force (lb)

0.5

0

0102030406070809010

Wheel Travel (mm)

Less Firm

50

MAINTAINING AND STORING YOUR T-MAXX

Your T-Maxx requires timely maintenance in order to stay in top running
condition. Neglecting the maintenance could allow dirt, deposits, and

moisture to build up inside the engine, leading to internal engine
failure. The following procedures should be taken very seriously.

After each hour of running:

•

Clean and re-oil the air filter. The instructions for this procedure are
on page 19. We cannot stress

air filter at the scheduled intervals. Do not neglect

enough the value of cleaning your

your air filter

maintenance!

•

Clean the outside of the engine of accumulated dirt, oil, and grime.
Accumulated grime will decrease the engine’s ability to cool itself.

After each running session:

•

Perform after-run maintenance on the engine. This clears the
engine of destructive moisture and other corrosive deposits. This

is extremely important for the life of the engine. See below for
after-run maintenance procedures.

• I

nspect the vehicle for obvious damage or wear. Look for:

1. Loose or missing screws

2. Cracked, bent, or damaged parts

3. Cut or loose wiring

4. Cut or kinked fuel lines

5. Signs of fuel leakage

•

Inspect the gears for wear, broken teeth, or debris lodged between
the teeth.

Other periodic maintenance:

•

Slipper clutch pegs (friction
material): The slipper clutch
pegs will wear over time and
require replacement. The life of
the pegs depends on how the
slipper clutch was adjusted and
how the T-Maxx was used. If the
slipper will not tighten or you are seeing signs of wear on the face
of the gear, then the pegs should be replaced.

•

Piston/sleeve:

with how the engine was used and maintained. The piston

The life of the piston and sleeve will vary greatly

and sleeve should be replaced when they no
longer seal effectively (loss of compression).
Symptoms include the engine being difficult
to start when warm, stalling when warm, and
stalling when throttle is suddenly closed to idle.
Replace the wrist pin and G-clip whenever the
piston and sleeve are replaced.

Connecting rod:

•

The connecting rod should
be replaced when the piston and sleeve
are replaced or after three gallons of fuel,
whichever comes first. Also replace the piston
wrist pin and G-clip whenever the connecting
rod is replaced. As with other internal engine
components, connecting rod life depends on
engine usage and the quality and frequency of
engine maintenance.

EZ-Start™:

•

The cush drive elements in the
EZ-Start drive unit should be inspected after
3-gallons of fuel. If the cush drive elements appear deformed
or hardened, then they should be replaced. Inspect the EZ-Start
gears for any signs of wear. Damaged gears should be replaced.
Coat the gears with a thin layer of white lithium grease.

After-run Procedure

You must perform after-run maintenance on your Traxxas engine
whenever the model will be stored for longer than a few hours. Taking
the time to prepare your engine for storage will reward you with
longer engine life, easier starting, and better performance.
When a nitro engine is shut off, some excess unburned fuel remains in
the engine. The methanol in model engine fuel is hygroscopic, which
means it easily attracts and absorbs moisture. This moisture can cause
rust and corrosion on the steel engine parts (crankshaft, bearings,
wrist pin, and starter shaft) if the fuel is not removed from the engine.
There are after-run oil products available from your hobby dealer or
you can use WD-40™, a common household lubricant. To ensure your
TRX 2.5 engine is protected from internal corrosion, use the following
procedure:

1. Whenever possible, shut off the engine by pinching the fuel line
closed. This allows most of the excess fuel to be consumed by
the engine. Be sure the throttle is in the idle position. You may

If the engine is worn or
damaged enough to require
replacing the piston,
sleeve, or connecting rod,
consider exchanging your
old engine for a brand new
engine under the terms of
the Traxxas Lifetime Engine
Replacement Plan (ERP). It
could save you time and
effort. Details are in your
model’s documentation
package.

The TRX 2.5 Racing Engine
is designed to be easy to
rebuild. Critical engine
components, such as the
crankcase, crankshaft, and
engine bearings, are made
to extremely high quality
standards and should under
normal circumstances outlast
multiple sets of pistons,
sleeves, connecting rods,
and wrist pins (reciprocating
assemblies).
It could be more economical
for you to continue to use
your good bearings and
crankshafts, and simply
replace the reciprocating
assembly as needed. Engine
assembly is not difficult and
replacing the reciprocating
assembly does not require
any special tools or skills.

17

T-MAXX • 33

MAINTAINING AND STORING YOUR T-MAXX

Denatured alcohol (available
from home centers and
paint supply stores) in a
spray bottle is an extremely
effective cleaner. Be sure
to wear safety glasses and
gloves when working with
denatured alcohol.

Be sure to follow proper
maintenance and storage
procedures to avoid damage
to your engine and other
components of your T-Maxx.

Don’t put the fuel from your
tank back into your fuel
jug. Dispose of it properly,
following city or county
regulations.

Always wear eye protection
when using compressed
air or spray cleaners and
lubricants.

34 • T-MAXX

have to pinch the fuel line closed for several seconds before the
engine stops.

2. Completely empty the fuel tank. Use your fuel-dispensing bottle
to suck out the old fuel. Do not mix the old fuel with your fresh
fuel supply. If you leave fuel in the tank, transporting or handling
your T-Maxx may cause fuel to run into the engine.

3. With the fuel tank empty and the throttle at the idle position, try
to start the engine. The engine will most likely start and run for
a few seconds as it uses up any fuel remaining in the engine and
fuel lines.

4. Once the engine stops, clean the outside of the engine with
compressed air or spray motor cleaner. Once the engine is clean
and dry, remove the glow plug power wire, glow plug, and air filter.

5. Open the throttle fully and spray a one-second burst of WD-40
into the carburetor and into the glow plug hole (Caution! Wear
safety glasses to prevent spray from getting into your eyes). If you
are using after-run oil, follow the manufacturer’s instructions.

6. Place a rag or paper towel over the engine to catch any WD-40
or after-run oil that may come out of the carburetor or glow plug
hole.

7. Connect the EZ-Start controller to the model and spin the engine
for 10 seconds.

8. Remove the rag or paper towel and repeat steps 5–7 two
more times.

9. Clean and re-oil the air filter so it will be ready for use next time.
See page 19 for air filter maintenance instructions.

10. Replace the glow plug, reconnect the glow plug power wire, and
reinstall the air filter.

Clearing a Flooded Engine

If the engine is primed for too long during startup, then it can become
flooded with fuel. When the engine is flooded, it will no longer turn
due to excess fuel in the combustion chamber preventing upward
movement of the piston. Use the following procedure to clear a
flooded engine:

1. Remove the blue glow plug wire.

2. Remove the glow plug and gasket with the glow plug wrench

supplied with your model. A 5/16 or 8mm nut driver will also work.

3. Turn the model upside down and plug in the EZ-Start controller.

4. Push the EZ-Start button for several seconds to clear the engine
of excess fuel. Do not look into the glow plug hole while the
engine is spinning or you could spray fuel into your face!

Turn the model over and reinstall the glow plug and gasket.

5.

6. Reconnect the blue glow plug wire to the glow plug.

7. Reconnect the EZ-Start controller.

8. Do not prime the engine. Pull the throttle to 1/2 throttle and push
the EZ-Start button. The engine should start immediately.

Piston

stuck at

“top dead center” (TDC)

“Top dead center” is the position where the piston is at the very top
of the tapered sleeve. Occasionally an engine can get “stuck” at this
position. This is most likely to happen on new engines during break-in,
but can also happen at other times. If the engine is stuck at TDC, use
the following procedure to release the piston from the sleeve:

1. Remove the glow plug using the included
tool or 8mm (5/16") nut driver and verify
that the piston is at the top of its stroke.

2. Use a flat blade screwdriver to rotate the
flywheel. Place the blade of the driver
into one of the grooves of the flywheel
and push down, turning the flywheel
counterclockwise when viewed from the
front. The flywheel should turn, unsticking

Top Dead Center

the piston from the sleeve.

3. Put two or three drops of light machine
oil into the glow plug hole to lubricate the
piston and sleeve. Do not use too much
oil. It will hydro-lock the engine. Verify the
starter will spin the engine with the glow
plug out.

4. Rotate the flywheel so the piston is at
bottom dead center and replace the glow
plug with the gasket. Reconnect the blue
glow plug wire.

5. You should now be able to start the engine
with the EZ-Start.

Bottom Dead Center

TROUBLESHOOTING YOUR T-MAXX

The following section addresses some very basic engine and
radio questions you may have about your T-Maxx. Most questions
arise from simple user errors or minor adjustments that are easy
to correct. If you can’t find a solution for your T-Maxx here, then
visit our Web site at www.Traxxas.com/support. There you will
find a much more extensive and detailed online troubleshooting
area. In addition, you may call Traxxas Customer Service at
1-888-TRAXXAS (outside the U.S., call [phone]).

Radio system does not work properly:

• If the power light on the transmitter does not come on,
check for proper battery installation and that the batteries
are new and/or fully charged. If the power light is blinking,
then the transmitter batteries are weak and should be
replaced. See page 10 for more details.

• If the transmitter light is on but the radio is still not responding,
check for proper installation of the receiver batteries and that
the batteries are new and/or fully charged. Check to make sure
the on/off switch on the model is in the on position. Finally,
if there is still no response, check the red and black wires that
connect the battery pack to the “batt” terminal on the receiver
(you will have to remove the receiver cover). Make sure the
wires are not pinched or damaged and that the plug is secure
in the receiver. See page 10 for more details.

Engine will not spin (EZ-Start will not turn the engine):

• If neither LED on the controller lights, the EZ-Start battery
could be discharged or improperly connected. Inspect and
recharge if necessary.

• If the glow plug LED lights and the motor LED does not,
then the EZ-Start controller is in protection mode. Allow the
controller to cool for at least three minutes. The circuitry
should automatically reset.

• Check to make sure the wires are connected to the EZ-Start
motor in the T-Maxx. The red wire should connect to the
positive motor terminal, indicated by a red dot next to
the terminal.

• The engine could be flooded. If too much fuel accumulates
in the combustion chamber at start up, the engine will
hydraulically lock. Follow the procedure on page 34 for
clearing a flooded engine.

• Check for binding at the engine flywheel. If you are not able
to turn the engine by hand, the engine could be flooded,
there could be binding in the clutch system, or there could
be internal engine damage. (Note: It is normal for the engine
to be extremely tight and hard to turn when the piston
reaches the top of the compression stroke.)

Engine extremely sluggish, hard to start, and will not idle
during tank 1 of the break in:

• It is possible that the factory adjusted break-in settings
on your carburetor are too rich for your geographic
location, atmospheric conditions, or fuel brand. Extremes
in temperature, humidity, barometric pressure, and
altitude can’t always be accounted for with a single high­speed needle setting. The symptoms described above
can occur when the air density is very low, such as in high
mountainous elevations and extremely cold temperatures.
Under these conditions, lean the fuel mixture slightly, 1/8
turn, to see if there is any improvement in starting and
idling. Only lean the fuel mixture just until the engine will
run and idle reliably and then proceed with the break in.

• The contents of different brands of fuel (other than Traxxas
Top Fuel) in combination with extreme atmospheric
conditions can also make the factory preset break-in settings
too rich and cause the symptoms described above. Again,
try leaning the fuel mixture slightly, 1/8 turn, to see if there
is any improvement in starting and idling.

Engine spins but will not start:

• If the engine is spinning but will not start, first check to
make sure that both the motor and glow plug LEDs on the
EZ-Start controller light when the button is depressed. If the
glow plug LED does not light, make sure the blue glow plug
wire is tightly connected and is not damaged in any way.
If the wire is good, then replace the glow plug. It is normal
for glow plugs to require periodic replacement. Only use
Traxxas heavy-duty long glow plugs (see your parts list).

• Check your fuel mixture settings. It may be necessary
to adjust the fuel mixture if the outside temperature or
barometric pressure has changed significantly since the last
time the engine was run (see Fine Tuning the Carburetor on

28). Turn the high-speed needle out (rich/counterclockwise)
1/4 turn, hold the throttle trigger at about 1/2 throttle and
try again to start the engine. Once started, retune the engine
for performance (see page 26).

• Check to make sure the fuel is getting to the carburetor.
Remove the fuel line where it connects to the carburetor
to see if there is fuel in it. If not, you may need to prime the
engine. Reconnect the fuel line and then refer to page 24 for
instructions on priming the engine.

• The engine could be worn. If the fit between the piston and
sleeve is loose, compression is reduced, and the engine will
be difficult to start when it is warm and may tend to stall
when running and when the throttle is closed suddenly to
idle. Engine life depends on many factors, including fuel
type, air filter maintenance, needle settings, and how the
engine was used. For example, if the engine was allowed
to ingest dirt from lack of air filter maintenance or running
through water, then the internal engine components could
wear out extremely fast.

• Glow plug may have failed. If using an EZ-Start, check to see if
the glow plug light is on during starting. If not, replace the glow
plug. If using a glow ignitor, remove and check the glow plug.

Engine performance sluggish:

• Engine performance depends mostly on the fuel mixture
settings and how they compensate for the current atmospheric
conditions. Before you suspect other failures with the engine,
richen the high-speed needle at least 1/4 turn and then retune
the engine for performance (see page 26).

• If the fuel mixture seems to be set correctly, make sure the
fuel is fresh. If the fuel is old or was left uncapped for a long
period, then some of the important fuel components could
have evaporated. Try new, fresh Traxxas Top Fuel.

• Try a new Traxxas glow plug. Sometimes a glow plug will
work well enough to start the engine, but will not be able to
deliver the engine’s full performance potential.

• Check to make sure there is no binding in the driveline that
would cause excessive loads on the engine.

T-MAXX • 35

141030 KC2230-R00

owner’s manual

MODEL 49104-1

6200 TRAXXAS WAY, McKINNEY, TX 75070

1-888-TRAXXAS