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 ST for repairs covered under warranty you should send your truck to:
Hobby Services
1610 Interstate Drive
Champaign, Illinois 61822
Attn: Service Department
Phone: (217) 398-0007 9:00 am - 5:00 pm Central Time M-F
E-mail: hobbyservices@hobbico.com
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 1998 Printed in USA DTXZ1046 For Kit DTXC0055/DTXD60**
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.........................................................3
Assembly of the Pre-Built Version............................................4
Preparing the Radio System .................................................4
Section 1: Steering Servo Assembly........................................4
Section 2: Assembling the Radio Tray .....................................5
Section 3: Installing the Throttle Servo....................................7
Section 4: Throttle & Brake Linkages.......................................7
Section 5: Radio Adjustments...................................................8
Section 6: Prepare the Engine ..................................................9
Section 7: Installing the Body Mounts ...................................10
Section 8: Finishing..................................................................11
Section 9: Carburetor Settings................................................11
Section 10: Breaking-In the Engine ........................................12
Section 11: Running the Engine .............................................12
Section 12: Engine Maintenance.............................................13
Section 13: Performance Tuning.............................................14
Section 14: Maintenance Tips .................................................14
Engine Trouble Shooting .........................................................15
Thank you for purchasing the DuraTrax Maximum ST. This
manual contains the instructions you need to build, operate,
and maintain your new nitro R/C truck. Read over this
manual thoroughly before building or operating the
Maximum ST.
When the safety precautions are followed, the Maximum ST
will provide years of enjoyment. Use care and good sense
at all times when operating this radio controlled truck.
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 ST near people.
Spectators
should be behind the driver or at a safe distance away
from the vehicle.
• The engine and exhaust produces quite a bit of noise. If
you are disturbed by the amount of noise this truck
produces, wear ear protection such as earplugs. Do not
run this vehicle when or where it can disturb others.
• The engine and exhaust 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 truck 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 ST to take the rough
and tumble abuse that makes R/C trucks 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 truck. Just
send in the part to us and we will send you a Free
replacement. Please see the Maximum ST 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 ST repaired for a small charge by the experts
at DuraTrax’s authorized repair facility, Hobby Services,
at the address listed on the front page of this manual.
To speed up the repair process, please follow the
instructions listed below.
1. Under most circumstances return the ENTIRE system:
truck 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.
REPAIR SERVICE
STRESS-TECH™PARTS GUARANTEE
HELPFUL HINTS
SAFETY PRECAUTIONS
INTRODUCTION
TABLE OF CONTENTS
2
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.
To operate the Maximum ST these items are required:
• Glow plug starter (Hobbico Hot-Shot -HCAR2505).
• Fuel bottle (DuraTrax Kwik-Pit Bottle - DTXP0125)
• Fuel (DuraTrax Red Alert fuel - DTXP0520)
• Glow plug (O.S®. #A3 plug - OSMG2690)
• Glow plug wrench (DTXR1170)
• It is also helpful to have a couple of extra glow plugs
on hand.
(All of these items are available in a Nitro Starter Pack
from DuraTrax - DTXP0200).
For the Pre-Built version of the Maximum ST, 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 or diagonal cutters (HCAR0630)
• Hobby knife (HCAR0105), #11 blades (HCAR0211)
❏ 1. Remove the 4-cell battery holder. Place 4 “AA” batteries
(included)
in the holder. Remove the battery door from the bottom of the
transmitter and install 8 “AA” batteries into the battery holder. See the
radio instruction manual for details. Use a tie-strap to secure the
battery holder to the radio tray. See steps 8 and 9 of the “Assembling
The Radio Tray” section.
❏
2. Install the air cleaner with the tie-strap. These parts are in the
box that the transmitter was strapped to. See Step 4 of the “Prepare
the Engine” section.
❏
3. Remove the clear covering on the outside of the body. See Step
2 of the “Finishing” section.
❏ 4. Apply decals to the body. See Step 3 of the
“Finishing” section.
❏ 5. Mount the body. See Step 4 of the “Finishing”
section.
❏ 6. Before running your Maximum ST read the entire manual, especially
the “Running the Engine” section and watch the included video.
FINISHING THE RTR VERSION
TOOLS YOU WILL NEED
REQUIRED ITEMS FOR COMPLETION
SCREW INFORMATION
SPECIFICATION & DESCRIPTION CHANGES
3
M3x14
M3x14 Screw
3mm
14mm
Self-Tapping
Screw
3mm
14mm
4
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 ST 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 (DTXC0055)
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
truck.
❏ 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. 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 bottom of the radio tray. To find the
bottom of the radio tray, put the large circular hole to the
upper left as shown.
❏ Step 3. Attach the switch from your radio system so it
protrudes on the top of the servo tray (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
insert the screws from the top.
SECTION 2: ASSEMBLING THE RADIO TRAY
5
❏ Step 4. Attach the radio tray mounts as shown to the
chassis with (4) 3 x 8mm self-tapping screws.
❏ Step 5. 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 radio tray is shown temporarily inverted.)
❏ Step 6. 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 considerably longer than the
antenna tube. DO NOT CUT OR COIL THE ANTENNA.
Use tape to
attach the leftover antenna wire to the outside of
the
antenna tube.
❏ Step 7. Attach the radio tray to the radio posts with (4)
3 x 8mm self-tapping screws.
❏ Step 8. Remove from your radio system the 4-cell
receiver
battery holder and install (4) “AA” batteries. Plug
the
connector on the receiver battery holder into the
connector on
the switch. Make sure the switch is in the OFF position.
❏ Step 9. Place the receiver battery holder on top of the
radio tray and wrap a tie-strap around the receiver and the
receiver battery. Tighten the tie-strap until the receiver
battery is firmly in place. Cut the loose end of the tie-strap
leaving some excess to allow for removal of the strap for
battery replacement.
6
❏ Step 1. From bags PA001 and PA003, remove the (2)
throttle
servo mounts, (2) servo mount spacers, (4) 3 x 8mm
self-tapping screws, and (4) 3 x 15mm self-tapping screws.
❏ Step 2. Snap together the servo mounts and the servo
mount spacers by placing the servo mount spacer on the
bottom of the servo mount and then rotating the spacer into
place.
❏ Step 3. Use the (4) 3 x 8mm self-tapping screws to attach
the throttle servo to the throttle servo mounts.
❏ Step 4. Use the (4) 3 x 15mm 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. Install the rod connector in the last hole on one
arm (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
7
3/4"
(18mm)
❏ 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).
❏ Step 4. Place the servo arm on the throttle servo 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 truck.
❏ 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 collar.
Install a 3 x 3mm set screw in each of the 2mm collars. Do
not tighten the set screws all the way.
• 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
❏ Step 1. 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
❏ Step 1. A) With the radio system still on, set the throttle
in the neutral position.
B) Remove the X-shaped 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 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
8
E) Push the throttle rod with your finger so that the carb will
be nearly closed.
F) Move the throttle spring next to the rod connector.
G) Tighten the inner 2mm collar next to the throttle spring
without compressing the spring.
H) Tighten the outer collar on the throttle rod right next to the
rod connector.
I) Replace the throttle servo arm screw.
❏ Step 1. From bag P001, remove the fuel line, air cleaner,
and tie-strap.
❏ Step 2. Remove the fuel tank by taking out the two
screws on the bottom of the chassis.
❏ 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. Soak the air cleaner with an air filter oil, light
machine oil, or in a pinch, shock oil. Thoroughly soak the
foam element and squeeze out the excess. Place the air
cleaner on the top of the carb. Tighten a tie-strap around the
neck of the air cleaner to hold it on the carb throat and cut
off the excess portion of the tie-strap.
❏ Step 5. Re-install the fuel tank.
SECTION 6: PREPARE THE ENGINE
9
❏ Step 1. Cut out (4) body mounts, (2) body mount
brackets,
(1) bracket holder, (8)
body washers from the parts tree. You
will also need (4) 3 x 15mm self-tapping screws, (4) 3 x
12mm
self-tapping screws, and (4) 3 x 6mm self-tapping screws.
Rear Body Mount
❏ Step 1. Use the 3 x 15mm self-tapping screws to attach
the body mount bracket to the bracket holder. Attach it to the
third (middle) hole on the bracket holder. Pay attention to
the direction of the body mount bracket. The holes that will
attach the body mounts must face the rear.
❏ Step 2. Use (2) 3 x 12mm self-tapping screws to attach
the bracket holder to the rear of the gearbox.
❏ Step 3. Insert the body mounts through the holes in the
body mount bracket. It should be 1-9/16” (39mm) from the
top of the body mount to the top of the body mount bracket.
Use (2) 3 x 6mm self-tapping screws to hold the body
mounts to the body mount bracket. Make sure that the holes
for the body pins align front-to-rear (see photo).
Front Body Mount
❏ Step 1. Attach the body mount bracket to the front
support
with (2) 3 x 25mm self-tapping screws. Make sure that the
holes for attaching the body posts face the front.
❏ Step 2. Insert the body mount into the body mount
bracket. They should be 1-7/8" (48mm) from the top of the
body mount bracket to the top of the body mount. Attach the
body mounts with (2) 3 x 6mm self-tapping screws. Again,
make sure that the holes for the body clips are aligned frontto-rear.
SECTION 7: INSTALLING THE BODY MOUNTS
10
❏ Step 3. Snap in place the (4) body washers onto the (4)
body mounts.
❏ Step 4. Trim the body mounts under the body mount
brackets.
❏ 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. Use a body
washer on each body post and then secure the body to the
truck with (4) body clips.
Congratulations, you have completed assembly! Before
running your new truck, please take the time to carefully
read the instructions for 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
SECTION 9: CARBURETOR SETTINGS
SECTION 8: FINISHING
11
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
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 and 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 truck
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
truck, 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 3 to 6 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 second or two.
The First Tank
Your first tank of fuel should be running the truck 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
SECTION 11: RUNNING THE ENGINE
SECTION 10: BREAKING-IN THE ENGINE
12
the engine just barely runs. This may take a few times
adjusting the needle, running the truck away from you and
back, then adjusting the needle. The truck will perform
sluggishly and stall from time to time - that is normal.
4. Run the truck back and forth at medium speeds, slowly
accelerating and decelerating the truck.
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 truck 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).
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 truck back and forth. You should
notice that the truck will preform better during each run. Stop
the truck 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 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 use. 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 you will see some temperature
extremes.
If you are having problems with your engine consult the
engine troubleshooting flow chart on page 15. 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 ST.
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 surging. 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 on the needle seats 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
SECTION 12: ENGINE MAINTENANCE
13
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 truck. The
general rule is to have the suspension arms perfectly level
when the car is at rest. To determine the ride height, drop the
truck from around 6"-12" above flat ground. Drop the truck,
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
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 truck
track straight at high speed. Too much toe-in will make the
truck difficult to turn as well as reducing 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 truck. Positive
camber is where the tops of the tires are angled away from the
center of the truck. 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
ST 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 truck 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 30
and 50 weight will be best for your truck. 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. 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 truck, 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 truck
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 truck. 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 truck. Wipe off any oils that have collected on
the chassis, engine end exhaust. Oils will attract dirt on the
next run.
SECTION 14: MAINTENANCE TIPS
SECTION 13: PERFORMANCE TUNING
14
15
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.
RECOMMENDED ACCESSORIES
DuraTrax Bearing Completer Set
Reduce friction, drag and extend the life of your
Maximum ST’s parts with this ball bearing set.
Includes all sizes needed to replace the bushings
included with your Maximum ST. DTXC1090
DuraTrax Front/Rear Step Pin Tire
These tires are ideal for all-around off-road racing
excitement. DTXC8115
DuraTrax Hi-Flow Air Filter
This single-stage air filter provides superior
filtration with a tough, replaceable foam element.
DTXG2612
DuraTrax Nitro Starter Set
This set includes everything you need to start
racing. 5-way glow plug wrench, 1 qt. of Red Alert
fuel, Hobbico
®
glow starter w/charger, fuel bottle
and glow plug. DTXP0200
DuraTrax Crankshaft Locking Tool
Remove your engine’s clutch safely with this
easy to use, anodized metal tool. Works with all
.10 to .21 car and buggy engines. DTXR1100
DuraTrax XL Field Bag
Keep your gear loaded and race ready with the
XL field bag. Heavy duty black nylon bag with red
trim and white logo. DTXP2000
DuraTrax Deluxe Field Bag
Features include two zippered end compartments
plus a water-resistant bottom. Detachable
shoulder strap included. DTXP2010
DuraTrax Front Rib Tire
Add stability on straights and extra traction in
turns with this ribbed tire set. DTXC8000
DuraTrax Front/Rear Street Track Tire
When track conditions call for an out-of-theordinary tread, you need these special traction
tires. DTXC8005
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)
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