TRX 15 ENGINE MANUAL

User Manual: TRX-15-ENGINE-MANUAL

Open the PDF directly: View PDF .
Page Count: 12

INTRODUCTION

Thank you for purchasing a new Traxxas TRX

engine. This manual contains the instructions

you will need to operate and maintain your new

engine. Look over the manual and examine

the engine carefully before starting it. If for

some reason you think the engine is not what

you wanted, then do not continue any further.

Your hobby dealer absolutely cannot accept an

engine for return or exchange after it has been

run.

Please read this entire manual before

attempting to start your new engine. Even if

you are an experienced R/C enthusiast, please

continue reading to learn about the special fea-

tures that make the TRX engine unique. Pay

special attention to the break-in instructions

outlined in this manual. The engine must be

broken in (or “run in”) before maximum perfor-

mance can be achieved. Follow the directions

in this manual exactly. Do not be tempted to

takeashortcut here and immediately adjust for

top speed and acceleration. A comprehensive

rebuild section and a troubleshooting guide

have also been included.

If you have any questions about your new

engine, then call Traxxas’ technical support line

at 1-888-TRAXXAS (toll free, U.S.A. residents

only- outside U.S.A. call 972-265-8000).

Technical support is available Monday through

Friday, from 8:30am to 9:00pm Central

Standard Time. We hope that you will enjoy

your TRX engine for many hours to come.

HOW IT WORKS

The TRX engine is a two-stroke, air-cooled

design. It features “ABC” (Aluminum, Brass,

Chrome) type construction. The chrome sleeve

is tapered so that the aluminum piston feels

tighter at the top of the stroke than at the bot-

tom. The piston and sleeve are designed to

reach perfect running clearance when they

reach normal operating temperatures. The pis-

ton will feel tighter when cold.

Fuel enters the engine through the carbure-

tor where it is metered and mixed with air. The

fuel/air mixture is then drawn into the

crankcase. A rotating valve in the crankshaft

opens and closes the crankcase. On the pis-

ton’sdown stroke, the crankcase becomes

pressurized, and fuel is blown into the com-

bustion chamber through two timed intake

ports cut into the sleeve. Swirling action pre-

vents the fresh fuel/air mixture from exiting the

exhaust port. On the upstroke, the fuel is com-

pressed and ignited. When the engine is first

started, the electrically heated glow plug caus-

es the fuel to ignite. Once the engine is run-

ning, the fuel is ignited by a combination of

rapid compression (similar to a diesel) and

retained heat from the glow plug. Exhaust

gasses are evacuated through a third port in

the sleeve.

The contact surfaces of the engine are lubri-

cated by the oil carried in the fuel mixture. The

oil also helps to cool the engine. Some of the

oil is burned with the fuel mixture, producing

the characteristic smoketrail.

The ratio of air to fuel (mixture) is critically

important. Amixture that is too “rich” means

that there is too muchfuel, and a mixture

that is too “lean” means that there is not

enough fuel for the given amount of air.

When the mixture is too rich, performance will

be sluggish and there will be an excessive

amount of smoke. There is also a potential to

WARNING!

FAILURE TO FOLLOW THE PROCEDURES

IN THIS MANUAL COULD VOID YOUR

WARRANTY AND CAUSE PERMANENT

DAMAGE TO YOUR ENGINE.

TRX NITRO ENGINE

MANUAL

Covers:

TRX .12 and TRX Pro .15

2

foul the glow plug when the mixture is too rich.

When the mixture is too lean, there is not

enough fuel to cool or lubricate the internal

engine components, and damage to the engine

and a burned out glow plug is almost certain.

REQUIRED EQUIPMENT

To operate the engine, you will need the fol-

lowing equipment, which is available from your

hobby shop.

1. Glow starter (must be long enough to

reach the glow plug)

2. Model engine fuel (see fuel recommend-

ations)

3. Fuel dispensing bottle (or some way of

easily filling the vehicle’s tank, ie. fuel

bulb or pump.

4. Small phillips head and flat screwdrivers

(for making adjustments)

5. “AA” size batteries for your transmitter(8)

and receiver(4)

6. After-run oil

7. Spare glowplugs

8.Air-filter lube

GLOW STARTER

The glowstarter is a battery-powered device

used to heat the glowplug so that the engine

can be started. Once the engine is running,

the glowstarter is removed. The glow starter is

used even when the engine is hot.

FUEL

Fuel is the most critical component of mak-

ing your engine performproperly. Improper

fuels will cause hard starting, poor perfor-

mance,and excessive wear on the engine. At

the time of this publication, Traxxas has tested

and recommends the following fuels:

Blue Thunder

Byron’s Originals

Omega

Power Master

Other brands of fuel which are not listed may

also be used however, they must meet the fol-

lowing requirements completely.

CAUTION:

ALWAYS FOLLOW THE PRECAUTIONS

PRINTED ON THE CONTAINER OF FUEL.

KEEP IT AWAY FROM FLAMES AND

CHILDREN. THE MIXTURE IS FLAMMA-

BLE AND POISONOUS.

1. The fuel must contain both castor and syn-

thetic oils with a total oil content of 12 to 18%

2. 3-5% castor oil must be present in a syn-

thetic/castor blend fuel.

3. Nitromethane (nitro) content should try to be

kept between 10% and 20%.

The best fuels are castor/synthetic blends.

The castor provides high-temperature lubrica-

tion while the synthetic oils help prevent var-

nish build up. The best fuels also contain anti-

wear agents, anti-foaming agents, lubrication

additives, and rust and corrosion inhibitors.

Use fuels that are made for use in cars, not air-

planes. Car fuel will provide better throttle

response, easier tuning, and longer run times.

For more detailed information about fuels,

refer to the section on page 11, “More About

Fuels.”

FUEL BOTTLE

Fuel is usually purchased bythe gallon, so a

smaller bottle with a dispensing tube is

required to fill the fuel tank. Fuel tanks typical-

ly havecapacities from 75cc (car and truck) to

120cc (marine). The fuel bottle should be

capped to prevent the fuel from evaporating

and becoming contaminated with debris or

moisture. The alcohol and nitro contents of the

fuel will evaporate,thus upsetting the fuel bal-

ance and spoiling the fuel. Do not use fuel

which is old and/or discolored.

Aftermarket inline fuel filtersare avail-

able from your hobby shop and can be used

to insure a clean supplyof fuel for your

engine. Dirtis a serious threat to your engine.

RADIO SYSTEM OPERATION

Fully-assembled Traxxas models only.

Install the “AA” batteries into the battery

holder in your model. Tape the batteries into

the holder to prevent them from falling out dur-

ing rough driving. Wrap a rubber balloon over

the batteryholder to prevent fuel contamina-

tion, and to prevent the battery holder from

short-circuiting against the metal chassis.

Makesure the battery holder is held securely.

CAUTION:

KEEP THE FUEL CONTAINERS CAPPED

ATALL TIMES WHEN NOT IN USE. THE

FUEL CAN SPOIL VERY QUICKLY.

CAUTION:

Synthetic-only fuels are not designed for

ABC engines and can permanently dam-

age your engine. If you have any ques-

tions about fuels call us toll-free at

1-888-TRAXXAS.

3

1) Turn on the radio system, and make sure

the throttle and steering servos are operating

quickly and that none of the linkages are bind-

ing. When operating your model, always turn

the transmitter on first, followed by the receiv-

er in the model. After driving, turn off the

receiver first, and then turn off the transmitter.

NEVER TURN OFF THE RADIO WHILE THE

ENGINE IS RUNNING. (The on/off switch only

turns the receiver on and off. It does not turn

off a running engine.)

2) It is very important that all of the “AA”

radio system batteries are strong or fully

charged. DO NOT ATTEMPT TO OPERATE

THE MODEL WITH WEAK BATTERIES. IF

THE BATTERIES FAIL WHILE THE MODEL

IS IN MOTION, IT CAN CONTINUE TO RUN

OUT OF CONTROL.

3) Always check the routing of the battery

pack wires and their condition before each

use. A melted wire can cause a short-circuit

and lead to a loss of control.

4) Before start-up, have a friend help in

range testing the model’s radio to insure com-

plete control at the maximum distance from

the driver.

STARTING THE ENGINE

STEP 1: FILLING THE FUEL TANK

Use a small fuel bottle or bulb to put fuel

into the tank. Only fill the tank to the bottom of

the fill neck. The model can carefully be refu-

eled while the engine is running.

STEP 2: OILING THE AIR FILTER ELEMENT

The foam air filter element must be oiled

before running the engine. For the best fil-

tration, use the special type of oil made for

foam air filters. It should be available locally

from motorcycle shops and small engine

repair shops. Lightweight motor oil or after-run

oil mayalso be substituted. Saturate the filter

element with oil and then thoroughly squeeze

out the excess. For extremely dusty conditions,

special two or three-stage, pre-lubed filters are

available from Traxxas (Part #4062, and 4063).

STEP 3: HIGH-SPEED MIXTURE SETTING

The high-speed mixture screw controls how

much fuel enters the engine during mid and

high-speed operation. Turn the high-speed

mixture screw clockwise, by hand, until it stops

(Do not tighten or the needle may be dam-

aged). Now, turn the mixture screw counter-

clockwise 21/2complete turns.

Note: If you live in higher altitudes (1000

feet or higher above sea level), it may be nec-

essary for you to set your high-speed fuel

mixture as much as 1/2aturn leaner than out-

lined here. Call 1-888-TRAXXAS if you have

questions about setting your fuel mixture.

STEP 4: SETTING THE IDLE SPEED

The idle screw regulates the throttle open-

ing to control the idle speed The throttle open-

ing at idle should be set as shown in the draw-

ing. The opening should be 1 to 1 1/2millime-

ters at the widest point in the opening. The idle

speed may need to be readjusted after the

engine is warm.

STEP 5: LOW SPEED MIXTURE SETTING

This screw meters the fuel at low speeds.

The low-speed mixture screw is located in the

end of the carburetor, inside the throttle arm.

This screw controls how much fuel enters the

engine at idle and low throttle. This adjustment

will smooth the idle and improve acceleration

to mid speed. Make this adjustment with the

throttle closed, after setting the idle. Gently

turn this screw clockwise until it stops. Now

turn the low-speed mixture screw counter-

clockwise 13/4turns.

STEP 6: PRIMING THE ENGINE

Some models haveabutton on top of the

fuel tank, referred to as the prime button.

Pressing it will manually pump fuel into the

carburetor. Press the button several times until

4

the fuel moves through the hose up to the car-

buretor. Once the fuel has reached the carbu-

retor, press the button a few more times to

ensure that there is fuel in the engine. On mod-

els which are not equipped with a prime button

(such as marine), the engine may be primed by

holding your finger over either the carburetor

intake or the exhaust outlet(s) and pulling the

recoil starter. ALLOW A HOT ENGINE AND

EXHAUST TO COOL FIRST SO THAT YOU

DO NOT BURN YOURSELF. Pull until the fuel

reaches the carburetor and then pull one more

time to prime.

STEP 7: SHUTTING OFF THE ENGINE

To stop the engine, pinch and hold the car-

buretor’s fuel line while running at idle speed.

Do not shut the engine off by placing your fin-

ger over the exhaust outlet. On some models,

you can stop the engine by placing your shoe

against the flywheel where it protrudes through

the bottom of the chassis.

STEP 8: STARTING

Before starting your engine, read the

safety and mechanical engine precautions.

Turn the radio system on. Now, attach the

glow starter to the glow plug. Hold the model

firmly and pull the handle on the recoil starter

with short, quick pulls until the engine starts.

Do not extend the starter rope more than 12

inches, or pull it to its limit. This could dam-

age the starter. To prevent over extending the

starter, try resting your elbow against your

knee while bendig over to start the model. This

technique will make it difficult for you to have a

long enough stroke to over-pull the starter.

Note: Do not relate the starting of the TRX

engine to that of a lawnmower or weed trim-

mer. Those types of engines and starters are

completely different.

If the starter is difficult to pull, try loosening

the glow plug 1/4turn. This will reduce com-

pression and put less strain on the starter com-

ponents. Retighten the glow plug once the

engine starts.

Once the engine starts, do not let it yank the

starter handle from your hand. This could

cause the spring or the string to break.

CAUTION:

IF THE STARTER BECOMES LOCKED OR

DIFFICULTTOPULL, DO NOTFORCE IT

OR YOU COULD BREAK THE STARTER. A

STIFF OR LOCKED STARTER IS USUALLY

CAUSED BY ENGINE FLOODING.

If the engine does not start, then while

pulling the starter, open the throttle slightly by

either using the transmitter or by manually

pulling on the throttle arm adjustment collar.

If, after many tries, the engine still will not

start, there could be a problem with the glow

plug, glow starter, or the engine could be

flooded. Refer to the troubleshooting section

for more information. Any starting problems

are most likely fuel or glow starter related. Refer

to the Troubleshooting Guide for more detailed

information.

BREAKING-IN THE ENGINE

The key to breaking in your engine is

patience. During the break in period, your

engine may appear to malfunction with symp-

toms such as stalling, wildly inconsistent per-

formance, and fouled glow plugs. Don’t give up

on it! These are just “break-in pains” that every

new engine has to go through, and which will

disappear once you get through the break in

period. Just keep it running, and throttle on

and off as smoothlyas you can. Sudden

bursts or releases of the throttle can stall

your engine. Soon, after about the fourth tank

of fuel, your patience will pay off with solid,

consistent, performance.

The break in time will take about 1 to 11/2

hours. During this time, you should resist the

temptation to tune the engine for performance

and/or run for extended times at wide open

throttle. Completing the break in process as

instructed will result in the fastest, best per-

forming engine as compared to those engines

which were improperly broken in.

READ THIS BEFORE YOU BEGIN:

During break in, use fuel with the same per-

centage of nitro which you plan to run every

day. Do not use a lower percentage of nitro

during break in and then switch to a high-

er percentage for normal running.

THE ENGINE SHOULD BE BROKEN-IN

WHILE DRIVING THE MODEL ON A

SMOOTH, HARD SURFACE. For marine

engines, choose a body of water which is

clean and calm.

CAUTION:

TRX ENGINES MUST BE BROKEN-IN FOR

MAXIMUM LIFE AND HIGHEST LEVEL OF

PERFORMANCE. THIS PROCESS MUST

NOT BE SKIPPED. A SHORTCUT HERE

COULD SHORTEN THE ENGINE LIFE

5

AVOID BREAKING IN THE THE ENGINE ON

VERY HOT, HUMID DAYS. Wait until the

morning or evening when it is cooler.

Turn the high-speed mixture screw (needle)

clockwise (in) to lean the mixture. This

decreases fuel flow for the given amount of air.

Turn counter-clockwise (out) to richen the mix-

ture and increase the amount of fuel to be

mixed with the air.

BREAK-IN THE ENGINE WITH THE BODY

REMOVED FROM THE MODEL (FOR

EXTRA COOLING). You must not allow the

engine to overheat by running it with too lean

amixture or blocking the cooling air.

Overheating can cause severe engine damage.

DURING BREAK-IN, THE ENGINE CON-

SUMES A LARGE QUANTITY OF FUEL.

Watch the fuel level in the tank. As the fuel

level decreases, the engine will run leaner

which is undesirable during break in. If the

engine is allowed to run out of fuel while it is

running at speed, the glow plug could be dam-

aged and require replacement

During the break-in period the performance

level of the engine will be limited bythe rich

fuel mixture which is required. Once the

engine is fully broken-in (after about 4-6 tanks

of fuel) the mixture can be leaned out, and

speed and acceleration will increase.

Because of the rich fuel mixtures and the

wearing of the new parts, deposits will form on

the glowplug causing it to fail. Expect to

replace the glowplug possibly during the

break-in period, and definitely after the engine

is broken-in and the fuel mixture is leaned.

Glowplugs are consumable items which

have a tremendous effect on how your

engine performs. Keep a supply of extra

glow plugs available.

THE FIRST TANK OF FUEL

1. Set the high-speed and low-speed mixture

screws as described in STEPS 3 and 5. Once

the engine is started, drive the model slowly

for approximately 30 seconds to warm the

engine. Ease in and out of the throttle slow-

ly. If the engine keeps stalling when accelerat-

ing, then richen the high-speed mixture screw

to 23/4turns and/or the low-speed mixture

screw to 2 turns out from closed.

2. The idle speed should be set as fast as pos-

sible without causing the model to move. If

necessary, adjust as shown in Step 4 (page 3).

3. The baseline setting of the high-speed mix-

ture screw will vary slightly with each engine.

To know if your engine is set correctly for

break in, look for the following performance

characteristics (on a warm engine):

*The engine will accelerate sluggishly from a

standing start and may even try to stall if the

throttle is applied too quickly.

*Blue-white smoke will be emitted from the

exhaust.

*When the model is accelerating at full throt-

tle, the engine will never “clean out.” When an

engine “cleans out”, the speed and rpms will

increase suddenly and dramatically,as if the

engine has gone into “second gear.” Also the

amount of smokeemitted from the exhaust will

decrease.“Cleaning out” is a desirable

characteristic once the engine is broken-

in; however, during the first four tanks, try

to avoid it.

4. Alternate driving the model at medium

speeds and short(2-second) bursts of full-

throttle acceleration.

5. As the engine reaches normal operating

temperature, it will speed up and performance

will improve. This occurs because the fuel mix-

ture is becoming leaner with the increased

temperature. You will need to richen the fuel

mixture 150or more, so that the engine contin-

ues to run as described above. Tip:

Remember to keep the engine from “clean-

ing out” during break in by richening the

high-speed mixture as necessary.

6. When the first tank is almost gone, bring the

model in, shut off the engine, and allow it to

cool for 7-10 minutes before continuing.

7. Form the habit of inspecting the air cleaner

each time you refuel. Look inside the carbure-

tor for anysigns of dust entering the engine.

Removeany dust with a Q-tip and clean and

re-oil the filter.When the model is used in

extremely dusty conditions,use Traxxas 2-

stage (part#4062) or 3-stage (part #4063)

foam air filters.

6

TANKS 2-4

1. Turn the high-speed mixture screw clock-

wise 150and run through the second tank of

fuel. Repeat this process for the third and

fourth tanks of fuel as well. Important: Do not

lean the high speed mixture less than 2

turns out from closed (see illustration).

Also, be sure to allow the engine to cool

between each run.

2. During tanks 1-4, Watch closely for any

signs of overheating. These include:

- Steam or smoke emanating from the engine

surfaces

- Cleaning out and then lagging during high-

speed acceleration (as if running out of fuel)

- Popping or clattering sound when decelerat-

ing (detonation)

- Idle speed will surge or possibly diminish to

the point of stalling.

CAUTION:

IF THE ENGINE STALLS WHILE YOU ARE

DRIVING, BECAUSE OF AN OVERHEAT-

ING CONDITION, SEVERE DAMAGE MAY

HAVE ALREADY OCCURRED. OVER-

HEATING IS CAUSED BY THE FOLLOW-

ING OPERATIONAL ERRORS:

- FUEL MIXTURE IS SET TOO LEAN

- COOLING AIR FOR THE HEAD IS

BLOCKED

-EXCESSIVE NITRO CONTENT IN THE

FUEL

-INCORRECT OIL CONTENT IN THE FUEL

-POOR QUALITY FUEL

-EXCESSIVE LOADS PLACED UPON THE

ENGINE (caused byabound drivetrain

or driving in grass and deep sand)

YOUR ENGINE WILL BE SHORT-LIVED IF

ANY OF THE ABOVE CONDITIONS ARE

ALLOWED TO EXIST FOR ANY LENGTH

OF TIME.

TO TEST FOR OVERHEATING, place a drop

of water or spit on the top of the cylinder head.

If it sizzles away immediately, shut the engine

off at once. If it takes approximately 3-5 sec-

onds for the water drop to boil away, then the

engine is running within a normal temperature

range. Tip: On-board digital temperature

gauges are available from your hobby shop.

TUNING FOR POWER

Sometime between the fourth and sixth

tank of fuel, the internal engine parts should

be broken-in.You can then begin adjusting the

fuel mixture to maximize performance for your

normal driving needs.

The engine should never be run at more

than 90-95% of its maximum performance

capacity. As you continue to lean the fuel mix-

ture, the engine will run faster up to a point.

When the engine is set too lean, it will seem to

run strong at first, but will bog, hesitate, or stall

when running at high speed. The engine will

also rapidly overheat when the setting is too

lean. CHECK THE ENGINE TEMPERATURE

OFTEN AS YOU LEAN THE MIXTURE. DO

NOT LET THE ENGINE OVERHEAT.

At the optimum setting, the engine will clean

out; have a strong-sounding, high-pitched

whine at full speed; and there will be a thin trail

of whitish smokeemitted from the exhaust. It

is always better to set the engine a little

richrather than a little lean.

Find an area with a long smooth straight-

away that will allow the engine to run at full

throttle. Run the model two or three passes at

full throttle and note the top speed and accel-

eration. Turnthe high-speed mixture screw

clockwise 150and retest the model, again not-

ing the performance. Continue to lean the mix-

ture and retest the model until the highest

speed is achieved. At that point, turnthe mix-

ture screwcounterclockwise 15 to 300.This is

the optimum setting that the engine should be

run at.

If the engine stalls on acceleration,

begins to bog or slow down at full throttle,

or if there is a significant reduction in

exhaust smoke, then the engine is running

too lean. Immediately turn the high speed

mixture screw counterclockwise 450and oper-

ate the model at medium speeds for 1 or 2

minutes to allow the engine to cool. Then, con-

tinue testing. At no point should your high-

speed mixture needle be adjusted to fewer

than 2 turns out from the closed position.

7

TUNING THE LOW-SPEED

MIXTURE FOR PERFORMANCE

The low-speed mixture affects how the

engine will perform in the low and mid-rpm

ranges. Turning clockwise will lean the mix-

ture. As with the high-speed mixture, leaning

the low-speed mixture increases performance.

Again, if the mixture here is set too lean, the

engine may be starved for lubrication in the

low and mid-rpm ranges, thus causing over-

heating and excessive engine wear.

Perform the following test to determine if the

low speed mixture is set correctly. With the

engine warm and running, allow it to idle for

approximately 15 seconds. Now apply wide-

open throttle and note performance. If the

engine bogs, accelerates erratically, and a

large puff of blue smoke is emitted, then the

low speed mixture is too rich. Turn the screw

clockwise 150. If the engine speeds up

momentarily and then bogs, hesitates, or

stalls, then the low speed mixture is too lean.

Turn the screw counterclockwise 150. Adjust

the mixture screw in 150increments, wait 15

seconds, and retest after each change. Adjust

for the best acceleration without stalling.

ADJUSTING THE SLIPPER CLUTCH

Some Traxxas fuel-powered models are

equipped with an adjustable slipper clutch

which is built into the large spur gear. The pur-

pose of the slipper clutch is to regulate the

amount of power sent to the wheels in order to

prevent tire spin. When it slips, the slipper

clutch makes a high-pitch chirping noise,

which you should be able to hear over the

engine noise. When running on pavement, set

the clutch so that it is tight. When running on

dirt, slightly loosen the adjusting nut 1/8of a

turn out to reduce tire spin.

STORAGE

After running your model, use a good

“after-run” oil prior to storage. The

methanol used in the fuel attracts moisture

and can cause moisture and corrosion to form

inside the engine. Drain the fuel tank, attach

the glow starter and try to start the engine until

all of the remaining fuel is completely used up.

Remove the air cleaner and place the recom-

mended number of drops (usually 6 drops) of

the after-run oil into the carburetor. Now pull

the recoil starter 4 or 5 times to circulate the oil

and then replace the air cleaner. Never store

your model with unused fuel in it.

TROUBLESHOOTING:

GLOW PLUG PROBLEMS

The glow plug in your engine is a consum-

able item which must be replaced periodically

to maintain peak performance and starting

ease. Most often, any starting problems or

erratic performance can be traced back to

the glow plug. The glow plug should also be

suspected if the engine’s acceleration and

high-speed performance suddenly become

flat.

Aleaking glow plug can cause many prob-

lems with engine performance, especially if

the engine is not running well at speed. While

the engine is running, look for bubbles at the

base of the glow plug. Loosen the glow plug

and then re-tighten. If the problem persists,

remove the glow plug and replace it.

The only sure way to test for a faulty

glowplug is simply to install a NEW one to

see if the problem goes away. Remove the

plug from the cylinder head with a 5/16 inch nut

driver or socket. Make sure there is no dirt or

debris on the top of the head which could fall

down into the engine. Do not lose the copper

gasket which seals the glow plug. Touch the

glow plug to the contacts of the glow starter.

All of the coils should glow bright orange.

Sometimes the first few coils will not glow

while the rest are bright, most likely indi-

cating a bad plug. Do not perform this test in

direct sunlight. If the glow is dim orange, then

the glow starter battery should be replaced or

recharged.

Tip: Glow plugs can be damaged by run-

ning the fuel mixture too lean, applying

more than 1.5 volts to the plug, or by run-

ning out of fuel while the engine is running

at high RPMs.

Replacement glowplugs are available from

your hobbyshop or Traxxas. From the factory,

your engine was equipped with a standard

long-reach plug. For the best performance,

use the original Traxxas replacement plugs:

(part #3230, standard long plug for TRX .12 or

part #3231 heavy-duty long for TRX .15). Glow

plugs with idle bars should not be used.

Always use the new gasket which comes with

the glow plug. Do not use plugs with idle bars.

Tip: Traxxas heavy-duty glow plugs (part

#3231) should also be used in TRX .12s

equipped with tuned pipes. Do not use the

heavy-duty plug in a TRX .12 with stock

exhaust or poor performance may result.

8

FUEL PROBLEMS

Aclean, properly-lubed, air filter is essential

for maintaining the performance of the engine.

NEVER RUN YOUR ENGINE WITH A DRY

FILTER, OR WITHOUT THE AIR FILTER IN

PLACE. If dirt gets into the engine, all of the

internal parts can be severely damaged in a

short amount of time. INSPECT THE AIR FIL-

TER EACH TIME YOU REFUEL. The air filter

could become saturated with fuel when the

model is turned upside down, or when the

engine is flooded. The air filter should be

cleaned at the first sign of deterioration, oil

contamination, or blockage.

If you will be running your engine in

extremely dusty conditions or where there is

fine, powdery dust, then the Traxxas two-stage

oil/foam air filter (part #4062)or three stage fil-

ter (part #4063) should be used.

Your engine consumes more fuel than you

might expect. It will run approximately 8-10

minutes on a tank of fuel. Run time will be

even less during break-in because of the rich

fuel mixtures. Try not to let the fuel level drop

below 1/4of a tank. When the fuel level is low,

the engine will begin to draw air in with the

fuel, as the fuel sloshes away from the fuel

pickup point in the bottom of the tank. The air

in the line causes erratic performance and rad-

ical leaning of the fuel mixture. In this case, the

engine may lean out, stall, and the glow plug

could be damaged.

The main component of model engine fuel

is methanol. Methanol will attract moisture

from the air when left uncapped. If the fuel is

left uncapped, for even a few days, it

should be disposed of. Also,fuel left open

will get dust in it, which can damage your

engine. Keep the fuel tightly capped at all

times and store it awayfrom direct sun-

light.

Poor quality fuels maylead to overheating

problems. If the methanol is not pure,or the

nitro content is composed of nitromethane and

nitropropane instead of nitromethane, you

could experience all types of running problems

in addition to destructive ash buildup inside

the engine. Also, if the fuel does not contain

both castor oil and high quality synthetic oil,

then the fuel will cause many problems and

should not be used. You simply MUST use a

fuel which meets the standards outlined in the

fuel requirements section of this manual.

Other types of fuel are unacceptable.

The TRX engine is designed to perform

best on nitro contents between 10 and 20%.

When the 20% mark is surpassed, all risk and

responsibility for engine performance

becomes your own. Engine temperatures will

increase when more nitro is used, with only

modest gains in performance, and a decrease

in engine life. Use less nitro in warm weath-

er, and more in cool weather. Perform the

following test to determine if you are using

enough nitro. Start the engine, allow it to warm

up, and disconnect the glow starter. If there is

no discernable drop in RPMs, then you are

using enough nitro. If the engine doesn’t idle

smoothly or as fast when the glow starter is

removed, then the next higher level of nitro

should probably be purchased on your next

gallon of fuel. This test assumes that the glow

plug is good (a bad glow plug will also cause

poor running when the glow starter is

removed) and the engine is broken in.

It is possible for the fuel lines to develop

cuts and pinhole leaks when the fuel lines

are removed from their fittings. These leaks

allow air in the line which interrupts the fuel

flow. If a leak is suspected, replace the lines

with new tubing. DO NOT BLOW ON THE

TUBES WITH YOUR MOUTH. MODEL FUEL

IS POISONOUS.

FLOODING:

Occasionally, you may accidentally flood

the engine. Symptoms of a flooded engine

include difficulty pulling the starter and muffled

sound coming from the exhaust. Remove the

glowplug with a 5/16 inch nut driver and then

remove the air cleaner. Turn the engine upside

down to drain any excess fuel out of the com-

bustion chamber and carburetor. Pull the recoil

starter 4-5 times to clear the engine. Be

extremely careful not to let the fuel spray into

your face!Turn the model back over, install the

glow plug, and re-prime the carburetor. The

engine should start and run normally.

CARBURETOR TIPS:

The carburetor, because of its simple

design, is very reliable. Its only enemy is dirt.

Dirtparticles become embedded in the needle

seats and prevent consistent mixture settings.

The carburetor should be suspected when a

sudden and persistent leaning of the fuel mix-

ture is observed (the engine may suddenly

speed up). T

odislodge the dirt particle, try

screwing the high and low-speed mixture

screws all the way in and then back out to their

original settings. If the engine doesn’t return to

normal operation, try backing the mixture

screws out several more turns and then use

the prime button to force fuel through the car-

buretor. Return the mixture screws to their

9

original position. The engine will be flooded

after this process so follow the steps in the

above paragraph to return the engine to nor-

mal. If the dirt particles are still not cleared,

then remove the carburetor and clean both the

high-speed and low-speed needles with dena-

tured alcohol. To prevent this from re-occur-

ring, replace the air filter with a new unit and

install a new in-line fuel filter between the car-

buretor and fuel tank.

FUEL MIXTURE TIPS:

The fuel mixture is the largest variable you

have to control while operating your engine.

Fuel brand, ambient temperature, and humidi-

ty all effect how your mixture should be set. If

the engine runs great one day but runs rich or

lean on another day, it is most likely the result

of a change in the air quality and temperature.

This should be expected and adjusted for.

STARTER PROBLEMS

Most starter problems result from pulling

the starter too far or after the engine has been

flooded and/or is in a “locked” condition. The

starter can be removed from the engine by

removing the four 3x6mm philips head screws

that fasten the housing to the engine. The

starter must be removed in order to perform

any service on it. Refer to rebuild steps 6-12

on pages 13-14 for starter service.

COOLING PROBLEMS

Engine overheating is most often caused by

running the engine too lean or because the

cooling air for the cylinder head is blocked. If

the mixture is too lean, simply allow the engine

to cool, richen the mixture, and try again (both

the high-speed and low-speed mixtures have

an effect on running temperatures). Truck,

buggy,and car bodies must haveholes cut in

them to allowcooling air to moveacross the fin

surfaces of the cylinder head. On some bodies,

the windshield should be cut out so that air

can flowto the head. Additional cooling can be

achieved bycutting an opening in the backof

the body so that air will pass completely

through the body.

If the fuel meets all of the requirements,the

mixture is set rich, the head is receiving ade-

quate ventilation, and the engine continues to

overheat, then the model may have a bound-

up drivetrain. Look for dirty wheel bushings

which may have tightened or any other moving

part which may be causing excess drag on the

model. Driving through deep sand and grass

will also put excessive loads on the engine.

CHANGING CLUTCH BELLS

The clutch bell gear will wear from use and

should be changed periodically. The gear

should be replaced when the teeth on the gear

are sharp and pointed rather than square-

shouldered. Metal particles become embedded

in the spur gear and it should be replaced at

this time also. Refer to engine rebuild steps

and the exploded-view drawing when disas-

sembling the clutch mechanism (the numbers

in parenthesis are part identification numbers).

MAINTENANCE

CONNECTING ROD

The connecting rod inside the engine

should be inspected for wear about every gallon

of fuel. We recommend that the connecting rod

be replaced if it shows wear. See engine

rebuild steps 1-5. If your engine is being used

in an application that requires continuous

high-speed operation, or if a lean fuel mixture

has been used to gain performance, then the

connecting rod should be checked more often.

Follow the step-by-step instructions in the

rebuild section of this manual to inspect or

change the connecting rod. Failure to inspect

the connecting rod at the prescribed intervals

could result in severe internal engine damage.

AIR CLEANER

The air cleaner is essential for keeping dirt

out of the engine. The air cleaner should be

inspected carefully every time you refuel. It

should be cleaned and re-oiled whenever it is

dirty. If you will be running your engine in

extremely dusty conditions or where there is

fine, powdery dust, then the Traxxas two-stage

oil/foam air filter (part #4062)or three stage

filter (part #4063) should be used.

CLEANING

The engine should be kept clean of oil and

grime for more effective cooling. The more

often the engine is cleaned, the easier it will be

to clean the engine. The easiest and most

effective cleaning method is to use dena-

tured alcohol applied with a trigger spray

bottle. Denatured alcohol is available from

paint and hardware stores and it will not attack

the plastics used in the construction of your

model. THE DENATURED ALCOHOL IS

FLAMMABLE SO KEEP IT AWAY FROM

OPEN SPARKS AND FLAME. FOLLOW ALL

OF THE PRECAUTIONS ON THE CONTAIN-

ER. Remove the batteries and radio system

from your model before spraying it with the

10

cleaner. Tilt the model up so that the alcohol

will dissolve the grime causing it to run off the

back of the model. The alcohol will then evap-

orate leaving little residue.

STORING YOUR MODEL

Use an after-run product in the engine

whenever the model is going to be stored and

whenever it has been cleaned with alcohol.

Use of the after run oil is described on page 7.

The denatured alcohol and the alcohol in the

fuel attracts moisture so the oil is needed to

prevent rusting and corrosion. Clean the

model as thoroughly as possible. Clean and oil

the bushings in the front wheels and rear

axles. Store unused fuel in a tightly-capped

container away from direct sunlight.

PRECAUTIONS

If the precautions are followed and your model

is operated sensibly and with care at all times,

it poses very little danger to you or your spec-

tators. Failure to operate your model in a safe

and responsible manner could result in prop-

erty damage and injury. You alone must see to

it that the instructions are followed and that the

precautions are adhered to.

PERSONAL PRECAUTIONS

* The fuel is dangerous. Follow all of the direc-

tions and precautions on the fuel container.

* The fuel can look like a cool drink to a young

child. Keep it out of children’s reach.

* The fuel is flammable Do not allow sparks,

flame, or smoking in the presence of model

fuel.

* The engine emits poisonous carbon monox-

ide gas just like a real automobile engine.

Always run the model in a well-ventilated

area. Never attempt to run the engine indoors

unless there is adequate ventilation.

*The engine, head, and exhaust system

become extremely hot during use. Be careful

not to touch these parts,especially when re-

fueling or reaching for the starter handle.

*Do not drivethe model at night, on public

streets, or in large crowds of people.

* Do not reach underneath a running model to

pickit up. You might accidentally come in

contact with the spinning flywheel.

*Fuel-powered models are very fast and can

cause injury if allowed to run into people or

animals. For this reason, it is very important

to maintain the mechanical integrity of the

model. The radio system, batteries, connec-

tions, and brakes should all be kept in good

working order so that they will be reliable.

* The engine produces a fair amount of noise.

Be considerate of your neighbors by not run-

ning your model early in the morning or late

in the evening. Try to find a place to run your

model where no one will be disturbed by its

noise.

MECHANICAL PRECAUTIONS

* The engine is capable of turning 30,000 or

more RPMs at full throttle. Continuous full-

throttle, high-speed operation will rapidly

decrease the life span of the internal

engine parts. For longer engine life, vary

your speed. If the engine will be run at

high speeds in a racing situation, expect

to replace worn parts more often.

* Do not attempt to operate the engine using

gasoline, alcohol, naptha, or any other fuel

other than model engine fuel.

* Do not allow the engine to overheat.

Overheating can damage the engine.

* Never run the engine without the air cleaner.

Inspect the air cleaner carefully each time

you re-fuel. Replace the air cleaner when

even the slightest signs of deterioration are

visible.

* Do not run excessively lean mixtures. A mix-

ture which is too lean will cause engine over-

heating and damage.

*If the engine performance suddenly changes,

stop at once and find the cause for the

change.

*Do not over-rev the engine. The engine will

over-rev if the throttle is fully opened while

the rear wheels of the model are off the

ground.

*If the model flips upside down, do not rev the

engine.

*Do not allow the engine to run out of fuel

while it is running at high RPMs. This could

damage the glowplug.

*Test the radio system each time before you

operate the model. Always use strong batter-

ies in the radio system. Stop running immedi-

ately at the first sign of weak batteries.

* Do not drive your model in thick grass or

deep sand. This puts excessive loads on the

engine and could cause it to overheat.

* Do not run your car, truck, or buggy through

water. The engine is not waterproof.

*The fuel used must meet the recommenda-

tions outlined in this manual. Failure to use

the correct fuel will damage the engine.

* The starter rope should not be pulled out

more than 12 inches. Longer pulls are not

necessaryand can damage the starter.

*Using fuels containing more than 20%

nitromethane will cause the engine to run

hotter and decrease its longevity.

11

MORE ABOUT FUELS

Do not use fuels blended with 100% syn-

thetic oils, without castor. Synthetic oils have

alower flash point than castor. Thus, when

the engine reaches its higher operating tem-

peratures, the synthetic oil may burn off the

bearing surfaces and not provide adequate

lubrication. This will result in severe damage

to your engine. When castor oil is present in

fuel, there is an extra margin of safety, provid-

ing for some measure of lubrication if the syn-

thetic oils have possibly burned away.

Also, do not use fuels blended with 100%

castor oil and no synthetic oil. 100% castor oil

will cause varnish to build up inside the

engine. The varnish coats the parts and pre-

vents effective heat transfer.

The purpose of the nitromethane in the fuel

is to increase the amount of fuel being burned,

thus improving power. The TRX-12 engine will

run on fuels which contain no nitromethane;

However, fuels containing 10-20%

nitromethane should be used. Increasing the

nitro content beyond 20% may improve power

up to a point; however, running temperatures

will also increase. A cool-running engine will

last longer and perform better.

There are several different types of “nitro”:

nitromethane, nitromethane, and nitro-

propane. Only use fuels with nitromethane in

model engines. Nitroethane and nitropropane

cause the engines to run very hot, but are

sometimes used in small percentages to lower

the cost of the fuel. Nitropropane is a known

carcinogen, and should be avoided.

The color in the fuel is simply for identifica-

tion purposes only. It has no effect on the per-

formance of the engine.

Do not buy fuel if you are unsure of its con-

tents. Proper fuel is absolutely vital for the life

and performance of your engine. Not all fuel is

created equal. If there is anydoubt about the

content of the fuel, the quality of the fuel, or

the reputation of the maker or seller, do not

buy it. Your best source for fuel is a reputable,

well-known hobby dealer who has experience

with small model engines. Always read the the

label, but generally speaking, nationally-rec-

ognized, brand-name fuels should have the oil

content you need.

During the break-in period, use the percent-

age of nitro which you plan to run every day.

Do not use a lower percentage of nitro during

break in and then switch to a higher nitro per-

centage for normal running.

12

Engine will not start

Starter will not retract

Starter will not pull

Engine starts and then stalls

Engine sluggish/ poor performance

Engine overheats

Engine hesitates or stumbles

Engine stalls instantly when throttle is

fully opened from idle

Engine stalls while driving around turns

Engine stalls while running for no

apparent reason

Out of fuel ..............................................

Improper or contaminated fuel ..............

Carburetor not primed ............................

Glow starter not charged ........................

Glow plug bad ........................................

Engine flooded........................................

Engine overheated ................................

Carburetor incorrectly adjusted ..............

Exhaust blocked ....................................

Air cleaner blocked ................................

No lubrication ........................................

Rope is jammed ....................................

Spring is unwound or broken ................

Engine is flooded....................................

Rope is jammed ....................................

Engine seized ........................................

Idle speed set too low ............................

Air bubble in fuel line ..............................

Glow plug is fouled or weak ..................

Engine overheated ................................

Insufficient fuel tank pressure ................

High-speed fuel mixture is too rich ........

Leaking glow plug ..................................

Glow plug is fouled or weak ..................

Fuel bad or contaminated ......................

Carburetor dirty or blocked ....................

Engine overheating ................................

Slipper clutch is improperly adjusted ....

Engine overgeared for application..........

Centrifugal clutch slipping ......................

Model has bound up drivetrain ..............

Engine excessively worn ........................

High-speed mixture too lean ..................

Cooling air is blocked ............................

Excessivenitro in the fuel ......................

Incorrect oil content in the fuel ..............

Poor quality fuel......................................

Excessive load on the engine ................

Low-speed mixture too lean ..................

High-speed mixture too lean ..................

Low-speed mixture too rich ....................

Engine overheated ................................

Air bubble in fuel line ..............................

Glow plug fouled ....................................

Insufficient fuel tank pressure ................

Glowplug fouled or weak ......................

Low-speed mixture too lean ..................

High-speed mixture too rich ..................

Fuel level is low ......................................

Idle speed set too low ............................

Glow plug fouled or weak ......................

Engine overheated ................................

Fuel line blocked with trash ....................

Insufficient fuel tank pressure ................

Fill fuel tank

Replace fuel

Prime carburetor

Charge glow starter

Replace glow plug- see “Glow Plug

Problems” section

See “Fuel Problems-Flooding” section

Allow engine to cool- find cause for overheating

Readjust carburetor

Remove and clean exhaust system

Clean air filter

Turn flywheel by hand to retract starter rope-

problem will correct itself after first run

Repair starter- see “Starter Problems” section

Repair starter- see “Starter Problems” section

Clear excess fuel- see “Flooding” section

Repair starter- see “Starter Problems” section

Disassemble engine to find cause

Increase idle speed

Use prime button to force bubble through-

check for a hole in the fuel lines

Replace glow plug- see “Glow Plug

Problems” section

Allow engine to cool- find cause for overheating

Replace pressure hose- Clear blockage at

exhaust header fitting- check flow to and

from tank

Set high-speed mixture to a leaner setting

Check glow plug gasket/ tighten glow plug

Replace glow plug- see “Glow Plug

problems” section

Replace fuel

Clean carburetor- see “Fuel Problems” section

Stop at once- find cause for overheating

Tighten slipper clutch (when equipped)

Use a lower gear ratio

Replace clutch shoes (return for service)

Find the bound item and repair

Return for service

Richen high-speed mixture

Direct air to the head

Use fuel with lower nitro content

Purchase correct fuel

Purchase correct fuel

Check for bound up drivetrain

Richen low-speed mixture

Richen high-speed mixture

Lean low-speed mixture

Stop at once- find cause for overheating

Use prime button to force bubble through-

check for a hole in the fuel lines or low fuel level

Test and/or replace glow plug- see “Glow

Plug Problems” section

Replace pressure hose- Clear blockage at

exhaust header fitting- check flow to and

from tank

Replace glowplug- see “Glow Plug

Problems” section

Richen low-speed mixture

Lean high-speed mixture

Refill fuel tank

Increase idle speed

Replace glow plug- see “Glow Plug

Problems” section

Stop at once- find cause for overheating

Replace fuel line- install fuel filter

Replace pressure hose- Clear blockage at

exhaust header fitting- check flow to and

from tank