Duratrax Maximum BX User Manual

Warranty

• DuraTrax®will warranty this kit for 90 days after the purchase date from defects in materials or

workmanship. DuraTrax

will either repair or replace, at no charge, the incorrectly made part.

• Make sure you save the receipt or invoice you were given when you bought your model! It is your proof of purchase
and we must see it before we can honor the warranty.

• To return your Maximum BX for repairs covered under warranty you should send your buggy to:

Hobby Services

1610 Interstate Drive

Champaign, Illinois 61822

Attn: Service Department

Phone: [phone]:00 am - 5:00 pm Central Time M-F

E-mail: [e-mail]

Before Building:

We want the building and operating of this vehicle to be a success, so BEFORE removing any parts from the parts bags
please read this manual thoroughly and watch the included video to familiarize yourself with the model. If for any reason
you think this model is not for you, return it to your dealer immediately. PLEASE NOTE: Your hobby dealer cannot accept
a return on any model after assembly has begun.

ASSEMBLY AND OPERATION MANUAL

© Copyright 1999 Printed in USA DTXZ1048 For Kit DTXC0060/DTXD65**

™

Introduction.................................................................................2

Safety Precautions .....................................................................2

Helpful Hints................................................................................2

Stress-Tech

™

Parts Guarantee...................................................2

Repair Service.............................................................................2

Specification & Description Changes.......................................3

Screw Information ......................................................................3

Required Items for Completion .................................................3

Tools You Will Need....................................................................3

Finishing the RTR Version.........................................................4

Assembly of the Pre-Built Version............................................6

Preparing the Radio System .................................................6

Section 1: Steering Servo Assembly........................................6

Section 2: Assembling the Radio Tray .....................................7

Section 3: Installing the Throttle Servo....................................9

Section 4: Throttle & Brake Linkages.......................................9

Section 5: Radio Adjustments.................................................10

Section 6: Prepare the Engine.................................................11

Section 7: Finishing .................................................................12

Section 8: Carburetor Settings................................................12

Section 9: Breaking-In the Engine ..........................................13

Section 10: Running the Engine .............................................13

Section 11: Engine Maintenance.............................................14

Section 12: Performance Tuning.............................................14

Section 13: Maintenance Tips .................................................15

Engine Trouble Shooting .........................................................16

Thank you for purchasing the DuraTrax Maximum BX. This
manual contains the instructions you need to build, operate,
and maintain your new nitro R/C buggy. Read over this
manual thoroughly before building or operating the
Maximum BX.

When the safety precautions are followed, the Maximum BX
will provide years of enjoyment. Use care and good sense
at all times when operating this radio controlled buggy.
Failure to use this vehicle in a safe, sensible manner can
result in injury or damage to property. You and you alone
must insure that the instructions are carefully followed and
all safety precautions are obeyed.

• Do not operate the Maximum BX near people.

Spectators
should be behind the driver or at a safe distance away
from the vehicle.

• The engine and exhaust system produces quite a bit of
noise. If you are disturbed by the amount of noise this
buggy produces, wear ear protection such as earplugs.
Do not run this vehicle when or where it can disturb

others.

• The engine and exhaust system can become very hot.
Avoid touching any of these parts during use and until
they have cooled down.

• Model engine fuel is poisonous. Make sure you read and
follow all of the precautions on the fuel container. Keep
fuel out of the reach of children.

• Model engine fuel is flammable and when ignited has a
flame that is difficult to see. Avoid sparks, flames,
smoking, or any other ignition source when fuel is near.

• The engine emits carbon dioxide just like real cars. Do
not operate this model indoors.

• Before turning on the transmitter, make sure that no one
else is on your frequency.

• Avoid working over a deep pile carpet. If you drop a small
part or screw, it will be difficult to find.

• Place a mat or towel over your work surface. This will
prevent parts from rolling off and will protect the work
surface.

• Avoid running the buggy in cold weather. The plastic and
metal parts can become brittle at low temperatures. In
addition, grease and oil become thick, causing
premature wear and poor performance.

• Test fit all parts before attaching them permanently.

We have engineered the Maximum BX to take the rough
and tumble abuse that makes R/C fun. We are so confident
of the quality and durability of the Stress-Tech™plastic parts
that we will replace any Stress-Tech plastic part you break
during the first 6 months you own the buggy. Just send in
the part to us and we will send you a Free replacement.
Please see the Maximum BX parts list for the items covered
under the Stress-Tech guarantee.

To receive your free replacement part please send the
following to the Hobby Services address listed on the cover
of this manual:

• The broken part must be included.

• The part number and description of the broken part.

• Dated copy of your invoice or purchase receipt.

• Your name, phone number and shipping address.

Repair service is available anytime.

• After the 90 day warranty, you can still have your
Maximum BX repaired for a small charge by the experts
at DuraTrax’s authorized repair facility, Hobby Services,
at the address listed on the cover of this manual.

REPAIR SERVICE

STRESS-TECH™PARTS GUARANTEE

HELPFUL HINTS

SAFETY PRECAUTIONS

INTRODUCTION

TABLE OF CONTENTS

2

To speed up the repair process, please follow the
instructions listed below.

1. Under most circumstances return the ENTIRE system:
buggy and radio. The exception would be sending in a
Stress-Tech part. See the instructions under Stress-Tech
Guarantee.

2. Make sure the transmitter is turned off, all batteries are
removed, and fuel is drained from the tank.

3. Send written instructions which include: a list of all items
returned, a THOROUGH explanation of the problem and
the service needed, and your phone number during the
day. If you expect the repair to be covered under
warranty, be sure to include a proof of date of purchase
(your store receipt or purchase invoice).

4. Also be sure to include your full return address.

All pictures, descriptions, and specifications found in this
instruction manual are subject to change without notice.
DuraTrax maintains no responsibility for inadvertent errors
in this manual.

Do not use too much force when tightening self-tapping
screws into plastic. Overtightening will cause the threads in
the plastic to strip. We recommend that you stop turning a
self-tapping screw when you feel some resistance as the
head of the screw comes in contact with the plastic. Avoid
using powered screwdrivers when assembling this kit. They
tend to overtighten the screws. Do not use thread locking
compound on any self-tapping screws. The thread locking
compound may damage the plastic. IMPORTANT: Use
thread lock on any fastener that is threaded into metal or
fastened with a nut. Vibration from the engine will cause the
screws to loosen if thread locking compound is not used.

The illustration above shows how to identify the types of
screws used throughout this instruction manual.

To operate the Maximum BX these items are required:

• Glow plug starter (Hobbico®Hot-Shot™-HCAR2505)

• Fuel bottle (DuraTrax Kwik-Pit™Bottle - DTXP0125)

• Fuel (DuraTrax Red Alert™fuel - DTXP0520)

• Air filter oil

• Tie straps

• Hobby knife with #11 blade (HCAR0105)

• Glow plug wrench (DTXR1170)

• It is also helpful to have a couple of extra glow plugs
on hand. We recommend the O.S®. #A3 plug

(OSMG2690)

(All of these items are available in a Nitro Starter Pack
from DuraTrax - DTXP0200).

For the Pre-Built version of the Maximum BX, you will also
need:

• 2-channel radio with (2) standard servos.

•

(12) “AA” batteries - (4) for the receiver and (8) for the
transmitter.

• Small bottle of thread locking compound (GPMR6060).

To assemble the Pre-Built version (DTXC0055), you will
need the following tools:

• Phillips head screwdriver

• Flat blade screwdriver

• Needle-nose pliers

• Wire cutters

• Hobby knife (HCAR0105), #11 blades (HCAR0211)

TOOLS YOU WILL NEED

REQUIRED ITEMS FOR COMPLETION

SCREW INFORMATION

SPECIFICATION & DESCRIPTION CHANGES

3

M3x14

M3x14 Screw

3mm

14mm

Self-Tapping

Screw

3mm

14mm

❏ Step 1. Remove the transmitter and buggy from the

box.

❏ Step 2. Remove the twist-tie from the receiver

antenna. (The receiver antenna looks like a bundled
thin wire that is attached to the receiver.) Thread the
receiver antenna underneath and through the hole in
the radio plate next to the receiver switch.

❏ Step 3. Remove the antenna tube from the parts

bag. Thread the receiver antenna through the antenna
tube. The antenna will be longer than the antenna
tube. DO NOT COIL OR CUT THE ANTENNA. Press
fit the antenna tube through the hole in the radio plate.
Use a small piece of tape to secure the end of the
receiver antenna to the antenna tube. TIP: Run the
antenna through your fingers to straighten out kinks
before running through the antenna tube.

❏ Step 4. Remove the air filter and tie strap from the

parts bag. Thoroughly soak the air filter foam with
some oil (not

included) and then squeeze out the excess

oil. A light

machine oil (like 3-IN-ONE™) will work well.
Special oils made for air filters are also available in
most hobby and motorcycle shops. Place the air filter
onto the carburetor and secure it in place with the tie
strap. Cut off the excess part of the strap.

❏ Step 5. Remove the four screws from the top of the

radio plate and remove the receiver battery holder.

❏ Step 6. Place 4 “AA” batteries into the battery holder.

Pay attention to the polarity on the batteries. The
bottom (negative) of the batteries should connect with
the springs in the battery holders.

❏ Step 7. Re-install the receiver battery holder under

the radio plate. Make sure that the receiver switch is in
the off position. Plug the connector on the receiver

4

FINISHING THE RTR VERSION

battery into the socket on the receiver switch. Tuck the
wires between the servo and receiver battery so they
will not get caught on anything.

❏ Step 8. Remove the transmitter antenna from the

holder and screw it into the hole on top of the
transmitter.

❏ Step 9. Slide open the battery door on the bottom of

the transmitter and remove the transmitter battery
holder.

Place 8 “AA” batteries into the holder in the
configuration molded into the plastic on the battery
holder. Re-install the transmitter battery holder into the
transmitter and re-install the battery door.

❏ Step 10. Turn on the transmitter using the switch on

the back (see the photo with Step 8), The green light
on the side of the transmitter should light up. If there is
no light on, turn the transmitter off and check to ensure
that the battery holder is making contact with the
copper contacts on the inside of the battery
compartment. Make sure the batteries are installed
correctly. Turn the transmitter on and check for the
green indicator light. If the green light appears, turn off
the transmitter.

❏ Step 11. Remove the plastic from the outside of the

body. Apply the decals if desired.

❏ Step 12. Remove the body clips from the

parts bag.

Place the body on the body mounts. On

each body

mount place a body clip.

Congratulations, you have completed preparations!
Before running your new buggy, please take the time to
carefully read the instructions and watch the video before
running and breaking-in the engine. Make sure you follow
the safety precautions and most of all...HAVE FUN!

5

6

1. Install the batteries in the transmitter and
the receiver battery holders.

2. Extend the transmitter antenna.

3. Connect the steering servo, throttle servo

and receiver battery to the receiver.

4. Extend the receiver antenna.

5. Adjust the servo trims of the transmitter to
the neutral position.

6. Switch on the transmitter.

7. Switch on the receiver.

8. Operate the steering and throttle control.
Make sure the servo arms move in
proportion to the movement of the
steering wheel and throttle trigger.

9. Switch off the receiver, then the transmitter.

Before installing the radio system in the
pre-built DuraTrax Maximum BX, read the
manufacturer’s instructions manual and
follow the instructions shown below.

Servo Arm

Steering
Servo

Throttle Servo

Receiver Battery Holder

4-AA Batteries

Transmitter

5

6

1

Antenna

4

8-AA Batteries

1

Receiver

3

Receiver
Switch

7

Antenna

2

8

PREPARING THE RADIO SYSTEM

ASSEMBLY OF THE PRE-BUILT VERSION (DTXC0060)

Place a check mark in the check boxes after each step is
completed.

❏ Step 1. From bags PA001 and PA003, remove (8) 3 x

8mm

self-tapping screws, and the (2) L-shaped servo mounts.

❏ Step 2. Attach the servo mounts to the steering servo

with (4) 3 x 8mm self-tapping screws.

Note that the servo

spline will mount towards the rear of the

buggy.

❏ Step 3. Attach the steering servo assembly to the chassis

with (4) 3 x 8mm self-tapping screws in the holes provided
as shown above.

SECTION 1: STEERING SERVO ASSEMBLY

❏ Step 4. From bag PA001, remove the steering rod. Note

the shape of the rod.

❏ Step 5. Use a 3 or 4 hole servo arm from your radio

system. A 1, 2, or 4-armed servo arm will work. Cut off all
but one of the arms by scoring both sides of the servo arm
with a hobby knife and using pliers to snap off the arm.

❏ Step 6. Put the steering rod into the third hole from the

center of the servo arm (approximately 5/8" or 16mm). You
may need to enlarge the hole in the servo arm with a 5/64"
(2mm) drill or a hobby knife.

❏ Step 7. Place the rod connector through the top of the

middle hole in the steering arm. Place a small amount of
thread locking compound onto the threads of the rod
connector. Install the 2mm nut onto the bottom of the rod
connector. Install a 2mm set screw into the top of the rod
connector. Note: When installing the set screw, make sure

not to thread it in too far because the steering rod must pass
through the hole on the side of the rod connector.

❏ Step 8. Slip the steering rod through the hole in the rod

connector that is already installed on the servo saver. (Use
the screw that came with your radio system to attach the
servo arm to the steering servo.) Do not tighten the set
screw on the rod connector. You will make the steering
adjustments later.

❏ Step 1. From bag PA002, remove all of the parts

included; the radio tray, the (2) radio tray mounts, and the
(8) 3 x 8mm self-tapping screws.

❏ Step 2. Using the provided double-sided tape, attach the

radio receiver to the top of the radio tray. To find the top of
the radio tray, place the large circular hole to the lower left
as shown. Make sure that the receiver is installed in the
space between the sets of screw holes as shown above.

SECTION 2: ASSEMBLING THE RADIO TRAY

7

❏ Step 3. Attach the switch from your radio system so it is

above the top of the radio plate (make sure the switch is in
the OFF position). Remove the two screws on the top of the
switch. Place the switch plate on top of the radio tray, the
switch body on the bottom of the radio tray and then reinsert
the screws from the top.

❏ Step 4. Place foam tape on the bottom of the radio plate.

This will secure the receiver battery into place when the
radio plate is installed.

❏ Step 5. Attach the radio tray mounts as shown to the

chassis with (4) 3 x 8mm self-tapping screws.

❏ Step 6. Remove from your radio system the 4-cell

receiver
battery holder and install (4) “AA” batteries. The negative
sides of the batteries are placed against the springs in the
battery holder. Plug

the connector on the receiver battery

holder into the

connector on the switch. Make sure the switch

is in the OFF position.

Place the receiver battery holder

between the radio plate

posts.

❏ Step 7. Plug the steering servo, throttle servo, and switch

into the receiver. See your radio instructions to determine
which channel is steering and which channel is throttle. The
receiver switch plugs into the socket labeled “Battery,”
“Batt,” or “B.”

❏ Step 8. Attach the radio tray to the radio posts with (4)

3 x 8mm self-tapping screws.

8

❏ Step 9. Fit the antenna tube through the radio tray and

press fit the antenna tube into the radio tray post. Thread
the receiver antenna through the antenna tube. The
receiver antenna wire will be longer than the antenna tube.
DO NOT CUT OR COIL THE ANTENNA. Use tape or cut
1/4" long pieces of fuel tubing to

attach the leftover antenna

wire to the outside of the

antenna tube. Use a hobby knife or
drill to cut a hole in the body to route the antenna tube
through.

❏ Step 1. From bags PA001 and PA003, remove the (2)

throttle

servo mounts and (8) 3 x 8mm self-tapping screws.

❏ Step 2. Use the (4) 3 x 8mm self-tapping screws to attach

the throttle servo to the throttle servo mounts.

❏ Step 3. Use the (4) 3 x 8mm self-tapping screws to attach

the throttle servo and the mounts to the chassis. Make sure
that the servo spline will be towards the rear.

❏ Step 1. From bags PA001 and PA003, remove the brake

rod, the throttle rod, the brake spring, (3) 3 x 3mm set
screws, the 2mm nut, the rod connector, and (3) 2mm
collars.

❏ Step 2. From your radio system remove a large,

X-shaped
servo arm. Remove two of the servo arms as shown. Install
the rod connector in the last hole on the arm as shown in the
diagram above (approximately 3/4" or 18mm). You will need
to enlarge the hole with a hobby knife or a 5/64" (2mm) drill
to fit the rod connector. Apply a small amount of thread
locking compound (not included), on the nut to hold it in
place. Secure the rod connector to the servo arm with the
2mm nut. Do not tighten the nut completely. The rod
connector should swivel easily.

SECTION 4: THROTTLE & BRAKE LINKAGES

SECTION 3: INSTALLING THE THROTTLE SERVO

9

3/4"

Rod Connector

(18mm)

Rod Connector

❏ Step 3. Insert the brake rod as shown in the photo. Insert

the brake rod into the servo arm from the bottom, into the
second hole from the outside of the arm (approximately 5/8"
or 16mm from the center).

❏ Step 4. Place the servo arm on the throttle servo as

shown in the photo above and place the brake rod through
the brake lever. Do not install the servo arm screw yet. You
will need to make adjustments before running your buggy.

❏ Step 5. Insert the throttle rod into the outer hole in the

carburetor arm. Assemble in order, a 2mm collar and the
throttle spring. Next insert the throttle rod through the rod
connector on the throttle servo.

❏ Step 6. Install a 2mm collar at the end of the brake rod

and another 2mm collar at the end of the throttle rod. Place

a small amount of thread locking compound on two of the
(3) 3 x 3mm set screws and thread them into the 2mm
collars. Do not tighten the set screws all the way. In the next
section we will make adjustments to the collars.

• Turn on the transmitter first, then the receiver.

• Center the trims of the throttle and steering channels (see

your radio system manual for the location of the trim
adjustments).

Steering Linkage Set Up

A) Remove the arm from the steering servo and re-install
the arm facing straight up (see photo above).

B) Position the front wheels so they are aimed “straight
ahead” (note that the tires are aligned slightly inward – this
is called toe-in).

C) When the wheels are straight, tighten the set screw on
the rod connector. Attach the servo arm with the servo arm
screw from your radio system.

Throttle Linkage Set Up

A) With the radio system still on, set the throttle in the
neutral position.

B) Remove the servo arm from the throttle and replace the
arm so that it is aligned with the centerline of the throttle
servo case.

C) The brake lever should be perpendicular (i.e. straight) to
the centerline of the chassis as shown above.

D) Tighten the 2mm collar on the brake rod so that it is 3/32"
(2mm) away from the brake lever.

SECTION 5: RADIO ADJUSTMENTS

10

E) Push the throttle rod with your finger until the carb closes
as far as possible (the carb will not close completely which
is normal).

F) Tighten the set screw on the outer collar and cut the
throttle rod flush with the outer 2mm collar.

G) Move the throttle spring next to the rod connector.

H) Tighten the inner 2mm collar next to the throttle spring
without compressing the spring.

I) Attach the throttle servo arm with the screw included with
your radio system.

❏ Step 1. Remove the fuel tank by taking out the two

screws on the bottom of the chassis.

❏ Step 2. From bag P001, remove the fuel line, air cleaner,

and tie-strap.

❏ Step 3. Cut the fuel line in half. Route one of the lines

from the nipple on the top of the muffler to the top of the fuel
tank. Route the other fuel line from the nipple on the
carburetor to the bottom of the fuel tank. Ensure that the fuel
line is not kinked anywhere along the line. You may have to
shorten the line to eliminate kinks.

❏ Step 4. Re-install the fuel tank.

❏ Step 5.

Remove the air filter and tie strap from the
parts bag. Thoroughly soak the air filter foam with
some oil (not

included) and then squeeze out the excess

oil. A light

machine oil (like 3-IN-ONE) will work well.
Special oils made for air filters are also available in
most hobby and motorcycle shops. Place the air filter
onto the carburetor and secure it in place with the tie
strap. Cut off the excess part of the strap

.

SECTION 6: PREPARE THE ENGINE

11

❏ Step 1. Bundle all of the wires around the receiver

together with a tie-strap or a twist-tie (not included in the kit).

❏ Step 2. Remove the clear covering from the outside of

the body.

❏ Step 3. Apply decals to the body if desired. For decal

placement, see the photos on the box top.

❏ Step 4. Mount the body on the body posts and secure the

body to the buggy with (2) body clips.

Congratulations, you have completed assembly! Before
running your new buggy, please take the time to carefully
read the instructions and watch the video before running
and breaking-in the engine. Make sure you follow the safety
precautions and most of all...HAVE FUN!

The High-Speed Needle

The “high-speed” needle is sticking up from the side of the
carb. It is located in the brass housing, just above the fuel
inlet. It controls the fuel to air mixture of the carb. The
needle is pre-set for break-in from the factory at 1-3/4 turns
out from the fully closed position of the carb. Once the
engine is broken-in, the high-speed needle would typically
run from 3/4 to 1-1/4 turns out from closed, depending on
the weather, humidity and altitude above sea level. To
richen turn the needle counterclockwise, to lean turn the
needle clockwise.

The Low-Speed Needle

The “low-speed” needle is the screw in the middle of the
throttle arm. It controls the fuel to air mixture at low throttle
settings. There is a simple way of adjusting the low-speed
needle correctly called the “pinch test.” With the engine at
idle, pinch the fuel line and listen to how the engine speeds

SECTION 8: CARBURETOR SETTINGS

SECTION 7: FINISHING

12

up or slows down. If the engine increases its speed for
about 2 or 3 seconds and then loses speed, the needle is
set correctly. If the engine loses RPM quickly, it is set too
lean and the low-speed needle needs to be opened
(counterclockwise) to richen the mixture. Pinch again

to

check the mixture. If the engine takes longer than 4

seconds
to slow down, lean (clockwise) the low-speed needle and
then pinch again to check the mixture.

The Throttle Stop Screw

On the front of the carburetor, there is a black screw. This is
called the idle stop screw. This increases or decreases the
idle RPM without changing the fuel to air mixture. The barrel
should be approximately 1.5mm (between 1/32" and 1/16")
from fully closed.

To insure long life and good performance from your Torq .12
engine, you MUST break-in the engine. The break-in period is
critical for long life of the internal parts of the engine. This
should be done over the first 4 or 5 tanks of fuel.

Some Things To Remember During Break-In

1. Run with the body off. This will keep the engine cooler.

2. Keep the air cleaner on at ALL times

3. Run on a smooth, hard surface. An empty parking lot is

perfect.

4. Use the same fuel that you will use for normal running.

5. Resist the urge to accelerate and decelerate the buggy

quickly.

6. Break-in puts stress on the glow plug and you can burn it

out during break-in. Make sure you have an extra plug or
two on hand.

7. Do NOT overheat the engine. You can check the head

temperature by using one of the temperature gauges that
are available or by putting a drop of water on the top of the
cylinder head. If the water boils away immediately, shut off
the engine and allow it to cool. If it takes more than 5
seconds to boil away, the engine is at proper running
temperature for break-in.

Before running the engine, read the manual and watch the
engine video that came with this kit.

There are several simple steps to starting the engine:

1. Install a glow plug. This threads into the top of the cylinder

head.

2. Fill the tank - Fill the tank almost to the top. Leave a little air

at the top of the tank.

3. Prime the engine - Use the primer button on the fuel tank to

force the fuel through the fuel line. Watch the fuel go
through the line and when it gets to the carburetor, press the
primer button once more to get fuel into the engine.

4. Open the high speed needle valve exactly 1-3/4 turns out

(counterclockwise) from fully closed. The high-speed
needle is sticking up from the carburetor inside the
brass housing. All of the carburetor settings are adjusted

with a flat bladed screwdriver. If you have previously run the
buggy, keep the same needle valve setting that you used on
your last run.

5. Start the engine by pulling the recoil - Use short, quick pulls.
DO NOT pull the recoil starter’s string to the end. You only
need 10 to 12 inches of pull to start the engine.

Sometimes it is helpful to start the engine at around half
throttle. Have a friend pull back on the throttle some while you
start the engine. This may be an indicator that the low speed
needle setting needs to be adjusted. When the engine starts,
immediately return the throttle to idle. If this is not done the
engine can over-rev and cause engine damage. If the engine

is difficult to turn over with the recoil starter, especially if
it is brand new, loosen the glow plug a half turn before
starting the engine. This allows some compression to
escape, but the engine will still start. Make sure you

tighten the glow plug after the engine starts. If the recoil
starter is still difficult to pull, the engine is flooded – there is too
much fuel inside the engine. Remove the glow plug and air
cleaner, then turn the engine upside down and pull the recoil 5
or 6 times. This will clear the engine of fuel, and you will notice
the recoil pulls easier. Replace the glow plug and repeat the
starting procedure.

Fuels

Use fuels that are specially formulated for car and truck
engines. DuraTrax Red Alert fuel is specially formulated for
buggy engines like the Torq .12.

How To Stop Your Engine

You may have been wondering how to stop the engine. All you
have to do is pinch the fuel line that runs to the carburetor and
from the bottom of the fuel tank. Pinching this will restrict the
fuel flow and the engine will quit within a few seconds.

The First Tank

Your first tank of fuel should be running the buggy at a very rich
high-speed needle valve setting. This allows the fuel to carry as
much oil as possible into the engine to lubricate the internal
parts during the break-in.

1. Open the needle valve 1-3/4 turns from fully closed

(counterclockwise). This is factory set already, but check it
to make sure. When closing the high-speed needle, close
the needle until you feel some resistance. DO NOT
overtighten or you will damage the engine.

2. Start the engine.

3. Once the engine is started, open the high-speed needle

valve around 1/8 turn at a time, finding the setting where
the engine just barely runs. This may take a few times
adjusting the needle, running the buggy away from you
and back, then adjusting the needle. The buggy will
perform sluggishly and stall from time to time - that is
normal.

4. Run the buggy back and forth at medium speeds, slowly

accelerating and decelerating the buggy.

5. After a minute or two of running, make sure the engine is

not overheating by putting a drop of water on the cylinder
head and watching it boil away. If it boils away
immediately, stop the engine and allow it to cool. Open the
high-speed needle around a 1/4 turn before starting again.
This is a good habit to get into every time you run to
ensure that the engine does not overheat during any run.
Looking at the smoke that comes out the exhaust is also
an indicator of how rich or lean the engine is running. If
there is a good amount of smoke coming out of the
exhaust, then chances are good that you are running rich.

6. Run the buggy back and forth at a medium speed until the

tank is almost out of fuel. Do not allow the tank to run out
of fuel. This leans out the engine and can cause
overheating (See How To Stop Your Engine).

SECTION 10: RUNNING THE ENGINE

SECTION 9: BREAKING-IN THE ENGINE

13

7. Stop the engine and allow the engine to cool before the
second tank. This normally takes around 10 minutes.

Tanks 2-5

Turn in the needle valve (clockwise) around 1/12 turn from the
previous setting. Run the buggy back and forth. You should
notice that the buggy will perform better during each run. Stop
the buggy periodically to check for overheating. If it is too hot,
stop the engine. Wait for it to cool, then open up the needle
valve and restart. After the 5th tank, you should be near to the
peak performance of the engine.

10 Ways To Ensure A Long Life From Your Engine:

1. Keep your engine clean. Dirt will act as insulation on an
engine. It will not be able to shed heat as easily. Use a
good air filter to keep dirt out of your engine and clean it
often.

2. Do not over-lean your engine.

3. Do not run your engine with little or no load. Don’t throttle
up the engine to full throttle when the wheels are not in
contact with the ground.

4. Do not overheat the engine. This goes along with keeping
it clean and not over-leaning the engine.

5. Do not use a fuel with a low oil content. Make sure you use
a fuel from a reputable manufacturer, such as DuraTrax
Red Alert.

6. Avoid using old fuels in the engine. Always run all of the
fuel out of the engine. After running for the day, use an
after-run oil and work it into the engine by turning the
flywheel or pulling the engine recoil slowly.

7. Do not use a fuel with a nitromethane (often called nitro)
content over 20%.

8. Do not scratch the piston or cylinder sleeve. Avoid
jamming something into the exhaust port when removing
or re-installing the clutch or flywheel. Use a special tool
called a crankshaft locking tool, which is installed in the
glow plug hole.

9. Do not use silicone sealer on the engine joints. Silicone
sealer contains acetic acid, which is corrosive if it gets
inside your engine.

10. Do not allow any water inside the engine. This sounds
easy, but temperature changes can cause

condensation

inside the engine. This is a good reason to use an after-

run

oil. Store your engine inside the house, not in a garage

or

shed where there will be temperature

extremes.

If you are having problems with your engine consult the
engine troubleshooting flow chart on page 16. The
following are some potential problems.

Glow Plug

The glow plug is an item that will wear out and need
replacement from time to time. It is a good idea to remove the
glow plug before your first run, heat it and see how well it
glows. You should see a bright orange glow from the filament.
If a coil or two will not glow or the plug will not glow at all,
replace the plug. If the engine quits when you remove the glow
starter, the plug might need to be changed, although this may
be because you are running too rich and need to screw in your
high-speed needle some. Look at the glow plug when you are
running the engine. If you see some bubbles coming from
around the plug, replace the glow plug (copper) gasket, or both
the plug and gasket. The only real way to test a glow plug is to
replace it. Make sure you have a spare plug or two on hand
every time that you run the Maximum BX.

Fuel

Fuel can go bad. The main ingredient in model fuel is
methanol, which is basically an alcohol. Alcohols can absorb
water out of the air, so keep your fuel jug capped at all times.
Store your fuel out of the sunlight and in a cool place. Bad fuel
is one of the most difficult problems to diagnose in engines. If
you have tried everything you can think of to remedy an engine
that is not running correctly, try using some fresh fuel.

Fuel line is susceptible to pinhole leaks. You cannot see the
hole in the fuel line, but if you see air bubbles in the line going
to the carburetor, replace the fuel line. Another symptom of a
leak in the fuel line is a surging engine. The properly tuned
engine will surge when the air bubbles hit the carb. It is
basically leaning out the mixture.

To keep dirt out of the engine, use an inline fuel filter on the fuel
line running from the fuel tank to the carburetor. Dirt can get
caught in the needle seat and cause an inconsistent running
engine. If you suspect that some dirt has lodged itself in the
carb, remove the needles and clean the carb

with denatured

alcohol or fuel. It can help to use

compressed air to blow out the
fuel passages as well. Dirt can get into your carburetor and
engine through the air filter. Ensure that your air cleaner has a
good seal to the top of the carb. Periodically wash the air
cleaner foam element and re-oil the filter. Any air cleaner that
has a torn element or a bad seal should be replaced
immediately.

Overheating

One of the worst things you can do to your engine is overheat
it. The oils that lubricate the engine are carried in the fuel. If
your engine is set too lean, there will not be enough oil in the
engine to lubricate the internal parts. This will cause premature
wear in the engine and cause damage. We have talked about
overheating in other parts of this manual, but we want to stress
the proper techniques to check for overheating. The easiest
way of checking the temperature of the cylinder head is using
one of the available temperature gauges. This will give you a
direct reading of the cylinder head temperature. Do not let the
head temperature exceed 220° Fahrenheit (104° Celsius).
Another way of checking the head temperature is to put a

drop

of water on the cylinder head. If it boils away

immediately, the
high-speed needle is set too lean. If the water boils away in
3-5 seconds, the engine is within proper operating

temperatures.
If the water boils away longer than 5 seconds, the mixture is set
rich which is preferable when breaking in the engine.
Otherwise lean the mixture some and retest after a minute of
running.

Ride Height: This refers to the clearance between the ground
and the chassis, both at the front and the back of the buggy.
The general rule is to have the suspension arms perfectly level
when the car is at rest. To determine the ride height, drop the
buggy from around 6"-12" above flat ground. Drop the buggy,
making sure it drops flat. Check where the suspension arms
come to rest. You can adjust ride by moving the spring
adjusters on the shock, which are at the top of each shock
spring, until the arms are level after the drop test.

Toe-In/Toe-Out: This refers to the angle of the front tires when
viewed from above when the suspension arms are level. If the
fronts of the tires angle in, it is called “toe-in” and if the fronts
of the tires angle out, it is called “toe-out.” This is adjusted by
turning the steering rods - the rods that run between the front

SECTION 12: PERFORMANCE TUNING

SECTION 11: ENGINE MAINTENANCE

14

hub and the servo saver. These are turnbuckle type, which
means you do not have to remove the rods to make
adjustments in length. Turning the rod in one direction will
lengthen, turning the rod the opposite direction will shorten.
Normally a small amount of toe-in is used to make the buggy
track straight at high speed. Too much toe-in will make the
buggy difficult to turn as well as reduce the overall top speed
because of tire scrub. Sometimes a small amount of toe-out will
be used to help the steering. As a general rule use a small
amount of toe-in.

Camber: Camber is the angle of the tops of the tires when
viewed from the front. Negative camber is when the tops of the
tires are angled towards the center of the buggy. Positive
camber is where the tops of the tires are angled away from the
center of the buggy. Positive camber is very rarely used, if ever.
A small amount of rear negative camber is helpful to increase
traction in the rear. Negative camber at the front will increase
stability. Camber adjustments can be made on the Maximum
BX by turning the “camber rods,” which are the upper links on
the suspension. The camber links are also turnbuckle type.
Lengthening the camber rod will add positive camber and
shortening the camber rod will add negative camber.

Shocks: Changes in shock oils, springs, and pre-load on the
springs can dramatically change the way the car handles. A
thicker shock oil will make the buggy turn faster but reduces
overall traction and handling over bumpy surfaces. Thinner oil
will increase traction at the expense of steering response and
the car will tend to roll more. In general, shock oils between 20
and 40 weight will be best for your buggy. You should
experiment some to see what oils work best for your track and
driving style. Shock springs affect the rate that the suspension
rebounds from a bump. We have supplied soft springs that
work under most conditions. Other springs are available from
DuraTrax. Pre-load on the springs means that the springs are
already compressed some so that the suspension will rebound
faster. Sometimes you will want to pre-load one side when the
track has turns all or mostly in one direction, for instance an
oval track. It will also increase the ride height.

Slipper Clutch: The slipper clutch is attached to the spur gear
on your buggy, the large gear on the outside of the
transmission. This clutch will slip when too much power is sent

to the wheels. It has adjustable tension by turning the nut on
the shaft. This is designed to maximize traction on various
surfaces by slipping before the wheels do. To adjust the slipper
clutch, run the buggy on the surface you plan to race. If the rear
wheels spin when full power is applied from a stop, loosen the
nut until the wheels do not spin any more. If the wheels do not
spin, tighten the nut until the wheels spin and then loosen the
nut some.

Before Each Run

• Check for loosened screws on the buggy. Engine vibration

will loosen some of the screws, particularly in the engine
mount area. Use thread lock on screws that thread into
metal parts or use a metal nut.

• Inspect the air cleaner for a torn or damaged element. Also

look for dirt in the air cleaner element and wash it if
necessary.

• Check the suspension and drive train for binding.

• Inspect all of the wires for damage. Also check the

connectors to make sure all of them are tight and in the
proper place.

• Check the fuel tank and fuel lines for leaks.

• Before starting the engine, turn on the radio and make sure

the servos move easily and in the right direction.

• Before running always check the condition of your radio

system batteries and replace/recharge if necessary.

After Each Run

• Drain the fuel tank of any leftover fuel. DO NOT return it to

your fuel jug.

• Put some after-run oil in the carb and turn the flywheel

several times to work the oil into the engine. This will protect
the engine from rusting, especially when stored for a long
period of time.

• Check again for loosened screws.

• CLEAN the buggy. Wipe off any oils that have collected on

the chassis, engine end exhaust. Oils will attract dirt on the
next run.

SECTION 13: MAINTENANCE TIPS

15

Inch Scale

0" 1" 2" 3" 4" 5" 6" 7"

0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180

Metric Scale (mm)

ENGINE TROUBLE SHOOTING

The engine starts

Does the engine
turn over easily?

Does it run

continuously?

Is fuel getting to

the engine?

Check for clogging in
the carburetor or fuel

line. Press the

primer pump and

check for fuel

spraying out of the

fuel line. If so,

replace the fuel line.

Is fuel in the

fuel line?

Is the glow plug

red hot?

Check the high speed needle
setting and prime the engine.

Is foreign matter
clogging the fuel

tank or fuel line?

Is the battery for

the glow plug
clip charged?

It should be
ready to go.

Is the high

speed needle

setting 1 to

1-1/2 turns out

from closed (if

the engine is

broken-in?)

Try starting the

engine again.

NO

NO

NO

NO

YES

YES

YES

YES

YES

Does the engine

quit when the

glow plug clip is

removed?

YES

YES

Clear the engine

of fuel.

NO

Reset the high

speed needle.

YES

NO

Replace the

glow plug.

Check that the

pressure line is

connected to the

muffler. The fuel

may be bad.

The engine does not start

NO

Does the engine

turn over easily

with the glow

plug removed?

The engine may

be flooded.

Clear the engine

of fuel.

YES

Check that

nothing is

caught in the

engine. Check

that the the

pull starter

operates

smoothly.

NO

Press the

primer pump

and check for

fuel spraying
out of the fuel
line through a

small hole. If

so, replace

the fuel line.

YES

Remove the

obstruction from

the fuel tank or

fuel line.

NO NO

Charge or

replace the

batteries.

YES

Replace the

glow plug.

Try starting the

engine again.