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INTRODUCTION

Thank you for purchasing a new Traxxas TRXengine. This manual contains the instructionsyou will need to operate and maintain your newengine. Look over the manual and examinethe engine carefully before starting it. If forsome reason you think the engine is not whatyou wanted, then do not continue any further.Your hobby dealer absolutelycannot accept anengine for return or exchange after it has beenrun.

Please read this entire manual beforeattempting to start your new engine. Even ifyou are an experienced R/C enthusiast, pleasecontinue reading to learn about the special fea-tures that make the TRX engine unique. Payspecial attention to the break-in instructionsoutlined in this manual. The engine must bebroken in (or run in) before maximum perfor-mance can be achieved. Follow the directionsin this manual exactly. Do not be tempted totake a shortcut here and immediately adjust fortop speed and acceleration. A comprehensiverebuild section and a troubleshooting guidehave also been included.

If you have any questions about your newengine, then call Traxxas technical support lineat 1-888-TRAXXAS (toll free, U.S.A. residentsonly- outside U.S.A. call 972-265-8000).Technical support is available Monday throughFriday, from 8:30am to 9:00pm CentralStandard Time. We hope that you will enjoyyour 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 sleeveis tapered so that the aluminum piston feelstighter at the top of the stroke than at the bot-tom. The piston and sleeve are designed toreach perfect running clearance when theyreach 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 thecrankcase. A rotating valve in the crankshaftopens and closes the crankcase. On the pis-tons down stroke, the crankcase becomespressurized, and fuel is blown into the com-bustion chamber through two timed intakeports cut into the sleeve. Swirling action pre-vents the fresh fuel/air mixture from exiting theexhaust port. On the upstroke, the fuel is com-pressed and ignited. When the engine is firststarted, the electrically heated glow plug caus-

es the fuel to ignite. Once the engine is run-ning, the fuel is ignited by a combination ofrapid compression (similar to a diesel) andretained heat from the glow plug. Exhaustgasses are evacuated through a third port inthe sleeve.

The contact surfaces of the engine are lubri-cated by the oil carried in the fuel mixture. Theoil also helps to cool the engine. Some of theoil is burned with the fuel mixture, producing

the characteristic smoke trail.

The ratio of air to fuel (mixture) is criticallyimportant. A mixture that is too rich meansthat there is too much fuel, and a mixturethat is too lean means that there is notenough fuel for the given amount of air.When the mixture is too rich, performance willbe sluggish and there will be an excessiveamount of smoke. There is also a potential to

WARNING!

FAILURE TO FOLLOW THE PROCEDURESIN THIS MANUAL COULD VOID YOURWARRANTY AND CAUSE PERMANENT

DAMAGE TO YOUR ENGINE.

TRX NITRO ENGINE

MANUAL

Covers:

TRX .12 and TRX Pro .15


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foul the glow plug when the mixture is too rich.When the mixture is too lean, there is notenough fuel to cool or lubricate the internalengine components, and damage to the engineand 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 yourhobby shop.

1. Glow starter (must be long enough toreach the glow plug)

2. Model engine fuel (see fuel recommend-ations)

3. Fuel dispensing bottle (or some way ofeasily filling the vehicles tank, ie. fuelbulb 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 oil7. Spare glow plugs8. Air-filter lube

GLOW STARTER

The glow starter is a battery-powered deviceused to heat the glow plug so that the enginecan be started. Once the engine is running,the glow starter is removed. The glow starter isused even when the engine is hot.

FUEL

Fuel is the most critical component of mak-ing your engine perform properly. Improperfuels will cause hard starting, poor perfor-mance, and excessive wear on the engine. Atthe time of this publication, Traxxas has testedand recommends the following fuels:

Blue ThunderByrons OriginalsOmegaPower Master

Other brands of fuel which are not listed mayalso be used however, they mustmeet 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 bekept 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, lubricationadditives, and rust and corrosion inhibitors.Use fuels that are made for use in cars, not air-planes. Car fuel will provide better throttleresponse, easier tuning, and longer run times.

For more detailed information about fuels,refer to the section on page 11, More AboutFuels.

FUEL BOTTLE

Fuel is usually purchased by the gallon, so asmaller bottle with a dispensing tube isrequired to fill the fuel tank. Fuel tanks typical-ly have capacities from 75cc (car and truck) to120cc (marine). The fuel bottle should becapped to prevent the fuel from evaporatingand becoming contaminated with debris ormoisture. The alcohol and nitro contents of thefuel will evaporate,thus upsetting the fuel bal-ance and spoiling the fuel. Do not use fuelwhich is old and/or discolored.

Aftermarket inline fuel filters are avail-able from your hobby shop and can be usedto insure a clean supply of fuel for yourengine. Dirt is 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 intothe holder to prevent them from falling out dur-ing rough driving. Wrap a rubber balloon overthe battery holder to prevent fuel contamina-tion, and to prevent the battery holder fromshort-circuiting against the metal chassis.Make sure the battery holder is held securely.

CAUTION:KEEP THE FUEL CONTAINERS CAPPEDAT ALL TIMES WHEN NOT IN USE. THE

FUEL CAN SPOIL VERY QUICKLY.

CAUTION:

Synthetic-only fuels are not designed forABC engines and can permanently dam-age your engine. If you have any ques-

tions about fuels call us toll-free at1-888-TRAXXAS.


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1) Turn on the radio system, and make surethe throttle and steering servos are operatingquickly and that none of the linkages are bind-ing. When operating your model, always turnthe transmitter on first, followed by the receiv-er in the model. After driving, turn off thereceiver first, and then turn off the transmitter.NEVER TURN OFF THE RADIO WHILE THEENGINE IS RUNNING. (The on/off switch onlyturns the receiver on and off. It does not turnoff a running engine.)

2) It is very important that all of the AAradio system batteries are strong or fullycharged. DO NOT ATTEMPT TO OPERATETHE MODEL WITH WEAK BATTERIES. IFTHE BATTERIES FAIL WHILE THE MODELIS IN MOTION, IT CAN CONTINUE TO RUNOUT OF CONTROL.

3) Always check the routing of the batterypack wires and their condition before eachuse. A melted wire can cause a short-circuitand lead to a loss of control.

4) Before start-up, have a friend help inrange testing the models radio to insure com-plete control at the maximum distance fromthe driver.

STARTING THE ENGINE

STEP 1: FILLING THE FUEL TANK

Use a small fuel bottle or bulb to put fuelinto the tank. Only fill the tank to the bottom ofthe 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 oiledbefore running the engine. For the best fil-tration, use the special type of oil made forfoam air filters. It should be available locallyfrom motorcycle shops and small enginerepair shops. Lightweight motor oil or after-runoil may also be substituted. Saturate the filterelement with oil and then thoroughly squeezeout 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 howmuch fuel enters the engine during mid andhigh-speed operation. Turn the high-speedmixture screw clockwise, by hand, until it stops(Do not tighten or the needle may be dam-aged). Now, turn the mixture screw counter-clockwise 2 1/2 complete turns.

Note: If you live in higher altitudes (1000feet or higher above sea level), it may be nec-essary for you to set your high-speed fuelmixture as much as 1/2 a turn leaner than out-lined here. Call 1-888-TRAXXAS if you havequestions 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 1/2 millime-ters at the widest point in the opening.The idlespeed may need to be readjusted after theengine is warm.

STEP 5: LOW SPEED MIXTURE SETTING

This screw meters the fuel at low speeds.The low-speed mixture screw is located in theend of the carburetor, inside the throttle arm.This screw controls how much fuel enters theengine at idle and low throttle.This adjustmentwill smooth the idle and improve accelerationto mid speed. Make this adjustment with the

throttle closed, after setting the idle. Gentlyturn this screw clockwise until it stops. Nowturn the low-speed mixture screw counter-clockwise 1 3/4 turns.

STEP 6: PRIMING THE ENGINE

Some models have a button on top of thefuel tank, referred to as the prime button.Pressing it will manually pump fuel into thecarburetor. Press the button several times until


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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 toensure 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 byholding your finger over either the carburetorintake or the exhaust outlet(s) and pulling therecoil starter. ALLOW A HOT ENGINE ANDEXHAUST TO COOL FIRST SO THAT YOUDO NOT BURN YOURSELF. Pull until the fuelreaches the carburetor and then pull one moretime to prime.

STEP 7: SHUTTING OFF THE ENGINE

To stop the engine, pinch and hold the car-buretors 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 shoeagainst the flywheel where it protrudes throughthe bottom of the chassis.

STEP 8: STARTING

Before starting your engine, read thesafety and mechanical engine precautions.

Turn the radio system on. Now, attach theglow starter to the glow plug. Hold the modelfirmly and pull the handle on the recoil starterwith short, quick pulls until the engine starts.Do not extend the starter rope more than 12inches, or pull it to its limit. This could dam-age the starter. To prevent over extending thestarter, try resting your elbow against yourknee while bendig over to start the model. Thistechnique will make it difficult for you to have along enough stroke to over-pull the starter.Note: Do not relate the starting of the TRXengine to that of a lawnmower or weed trim-mer. Those types of engines and starters arecompletely different.

If the starter is difficult to pull, try looseningthe glow plug 1/4 turn. This will reduce com-pression and put less strain on the starter com-ponents. Retighten the glow plug once theengine starts.

Once the engine starts, do not let it yank thestarter handle from your hand. This couldcause the spring or the string to break.

CAUTION:IF THE STARTER BECOMES LOCKED ORDIFFICULT TO PULL, DO NOT FORCE IT

OR YOU COULD BREAK THE STARTER. ASTIFF OR LOCKED STARTER IS USUALLY

CAUSED BY ENGINE FLOODING.

If the engine does not start, then whilepulling the starter, open the throttle slightly byeither using the transmitter or by manuallypulling on the throttle arm adjustment collar.

If, after many tries, the engine still will notstart, there could be a problem with the glowplug, glow starter, or the engine could beflooded. Refer to the troubleshooting sectionfor more information. Any starting problemsare most likely fuel or glow starter related.Referto the Troubleshooting Guide for more detailedinformation.

BREAKING-IN THE ENGINE

The key to breaking in your engine ispatience. During the break in period, yourengine may appear to malfunction with symp-toms such as stalling, wildly inconsistent per-

formance, and fouled glow plugs.Dont give upon it! These are just break-in pains that everynew engine has to go through, and which willdisappear once you get through the break inperiod. Just keep it running, and throttle onand off as smoothly as you can. Suddenbursts or releases of the throttle can stallyour engine. Soon, after about the fourth tankof fuel, your patience will pay off with solid,consistent, performance.

The break in time will take about 1 to 1

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hours. During this time, you should resist thetemptation to tune the engine for performanceand/or run for extended times at wide openthrottle. Completing the break in process asinstructed will result in the fastest, best per-forming engine as compared to those engineswhich were improperly broken in.

READ THIS BEFOREYOU BEGIN:

During break in, use fuel with the same per-centage of nitro which you plan to run everyday. Do not use a lower percentage of nitroduring break in and then switch to a high-er percentage for normal running.

THE ENGINE SHOULD BE BROKEN-INWHILE DRIVING THE MODEL ON ASMOOTH, HARD SURFACE. For marineengines, choose a body of water which isclean and calm.

CAUTION:

TRX ENGINES MUST BE BROKEN-IN FORMAXIMUM LIFE AND HIGHEST LEVEL OFPERFORMANCE. THIS PROCESS MUSTNOT BE SKIPPED. A SHORTCUT HERECOULD SHORTEN THE ENGINE LIFE


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AVOID BREAKING IN THE THE ENGINE ONVERY HOT, HUMID DAYS. Wait until themorning or evening when it is cooler.

Turn the high-speed mixture screw (needle)clockwise (in) to lean the mixture. Thisdecreases fuel flow for the given amount of air.Turn counter-clockwise (out) to richen the mix-ture and increase the amount of fuel to bemixed with the air.

BREAK-IN THE ENGINE WITH THE BODYREMOVED FROM THE MODEL (FOREXTRA COOLING). You must not allow theengine to overheat by running it with too leana mixture 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 fuellevel decreases, the engine will run leanerwhich is undesirable during break in. If theengine is allowed to run out of fuel while it isrunning at speed, the glow plug could be dam-aged and require replacement

During the break-in period the performancelevel of the engine will be limited by the richfuel mixture which is required. Once theengine is fully broken-in (after about 4-6 tanksof fuel) the mixture can be leaned out, andspeed and acceleration will increase.

Because of the rich fuel mixtures and thewearing of the new parts, deposits will form onthe glow plug causing it to fail. Expect toreplace the glow plug possibly during thebreak-in period, and definitely after the engineis broken-in and the fuel mixture is leaned.Glow plugs are consumable items whichhave a tremendous effect on how yourengine performs. Keep a supply of extraglow plugs available.

THE FIRST TANK OF FUEL

1. Set the high-speed and low-speed mixturescrews as described in STEPS 3 and 5. Oncethe engine is started, drive the model slowlyfor approximately 30 seconds to warm theengine. Ease in and out of the throttle slow-ly. If the engine keeps stalling when accelerat-ing, then richen the high-speed mixture screwto 23/4 turns and/or the low-speed mixturescrew to 2 turns out from closed.

2. The idle speed should be set as fast as pos-sible without causing the model to move. Ifnecessary, 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 forbreak in, look for the following performancecharacteristics (on a warm engine):* The engine will accelerate sluggishly from astanding start and may even try to stall if thethrottle is applied too quickly.* Blue-white smoke will be emitted from theexhaust.* When the model is accelerating at full throt-tle, the engine will never clean out. When anengine cleans out, the speed and rpms willincrease suddenly and dramatically, as if theengine has gone into second gear. Also theamount of smoke emitted from the exhaust willdecrease. Cleaning out is a desirablecharacteristic once the engine is broken-in; however, during the first four tanks, tryto avoid it.

4. Alternate driving the model at mediumspeeds and short (2-second) bursts of full-throttle acceleration.

5. As the engine reaches normal operatingtemperature, it will speed up and performancewill improve. This occurs because the fuel mix-ture is becoming leaner with the increasedtemperature. You will need to richen the fuelmixture 150 or 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 thehigh-speed mixture as necessary.

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

model in, shut off the engine, and allow it tocool for 7-10 minutes before continuing.

7. Form the habit of inspecting the air cleanereach time you refuel. Look inside the carbure-tor for any signs of dust entering the engine.Remove any dust with a Q-tip and clean andre-oil the filter. When the model is used inextremely dusty conditions, use Traxxas 2-stage (part #4062) or 3-stage (part #4063)foam air filters.


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TANKS 2-4

1. Turn the high-speed mixture screw clock-wise 150 and run through the second tank offuel. Repeat this process for the third andfourth tanks of fuel as well. Important: Do notlean the high speed mixture less than 2turns out from closed (see illustration).Also, be sure to allow the engine to coolbetween each run.

2. During tanks 1-4, Watch closely for anysigns of overheating. These include:

- Steam or smoke emanating from the enginesurfaces- 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 AREDRIVING, BECAUSE OF AN OVERHEAT-

ING CONDITION, SEVERE DAMAGE MAYHAVE 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 by a bound drivetrainor driving in grass and deep sand)

YOUR ENGINE WILL BE SHORT-LIVED IFANY OF THE ABOVE CONDITIONS AREALLOWED TO EXIST FOR ANY LENGTHOF TIME.

TO TEST FOR OVERHEATING, place a dropof water or spit on the top of the cylinder head.If it sizzles away immediately, shut the engineoff at once. If it takes approximately 3-5 sec-onds for the water drop to boil away, then theengine is running within a normal temperaturerange. Tip: On-board digital temperaturegauges are available from your hobby shop.

TUNING FOR POWER

Sometime between the fourth and sixthtank of fuel, the internal engine parts shouldbe broken-in.You can then begin adjusting thefuel mixture to maximize performance for yournormal driving needs.

The engine should never be run at morethan 90-95% of its maximum performancecapacity. 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 torun strong at first, but will bog, hesitate, or stallwhen running at high speed. The engine willalso rapidly overheat when the setting is toolean. CHECK THE ENGINE TEMPERATUREOFTEN AS YOU LEAN THE MIXTURE. DONOT LET THE ENGINE OVERHEAT.

At the optimum setting, the engine will cleanout; have a strong-sounding, high-pitchedwhine at full speed; and there will be a thin trailof whitish smoke emitted from the exhaust. Itis always better to set the engine a littlerich rather than a little lean.

Find an area with a long smooth straight-away that will allow the engine to run at fullthrottle. Run the model two or three passes atfull throttle and note the top speed and accel-

eration. Turn the high-speed mixture screwclockwise 150 and retest the model, again not-ing the performance. Continue to lean the mix-ture and retest the model until the highestspeed is achieved. At that point, turn the mix-ture screw counterclockwise 15 to 300. This isthe optimum setting that the engine should berun at.

If the engine stalls on acceleration,begins to bog or slow down at full throttle,

or if there is a significant reduction inexhaust smoke, then the engine is runningtoo lean. Immediately turn the high speedmixture screw counterclockwise 450 and oper-ate the model at medium speeds for 1 or 2minutes to allow the engine to cool. Then, con-tinue testing. At no point should your high-speed mixture needle be adjusted to fewerthan 2 turns out from the closed position.


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TUNING THE LOW-SPEED

MIXTURE FOR PERFORMANCE

The low-speed mixture affects how theengine will perform in the low and mid-rpmranges. Turning clockwise will lean the mix-ture. As with the high-speed mixture, leaningthe low-speed mixture increases performance.Again, if the mixture here is set too lean, theengine may be starved for lubrication in thelow and mid-rpm ranges, thus causing over-heating and excessive engine wear.

Perform the following test to determine if thelow speed mixture is set correctly. With theengine warm and running, allow it to idle forapproximately 15 seconds. Now apply wide-open throttle and note performance. If theengine bogs, accelerates erratically, and alarge puff of blue smoke is emitted, then thelow speed mixture is too rich. Turn the screwclockwise 150. If the engine speeds upmomentarily and then bogs, hesitates, orstalls, then the low speed mixture is too lean.Turn the screw counterclockwise 150. Adjustthe mixture screw in 150 increments, wait 15seconds, and retest after each change. Adjustfor the best acceleration without stalling.

ADJUSTING THE SLIPPER CLUTCH

Some Traxxas fuel-powered models areequipped with an adjustable slipper clutchwhich is built into the large spur gear. The pur-pose of the slipper clutch is to regulate theamount of power sent to the wheels in order toprevent tire spin. When it slips, the slipperclutch makes a high-pitch chirping noise,which you should be able to hear over theengine noise. When running on pavement, set

the clutch so that it is tight. When running ondirt, slightly loosen the adjusting nut 1/8 of aturn out to reduce tire spin.

STORAGE

After running your model, use a goodafter-run oil prior to storage. Themethanol used in the fuel attracts moistureand can cause moisture and corrosion to forminside the engine. Drain the fuel tank, attach

the glow starter and try to start the engine untilall of the remaining fuel is completely used up.Remove the air cleaner and place the recom-mended number of drops (usually 6 drops) ofthe after-run oil into the carburetor. Now pullthe recoil starter 4 or 5 times to circulate the oiland then replace the air cleaner. Never storeyour 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 periodicallyto maintain peak performance and startingease. Most often, any starting problems orerratic performance can be traced back tothe glow plug. The glow plug should also besuspected if the engines acceleration andhigh-speed performance suddenly becomeflat.

A leaking glow plug can cause many prob-lems with engine performance, especially ifthe engine is not running well at speed. Whilethe engine is running, look for bubbles at thebase of the glow plug. Loosen the glow plugand then re-tighten. If the problem persists,remove the glow plug and replace it.

The only sure way to test for a faultyglowplug is simply to install a NEW one tosee if the problem goes away. Remove theplug from the cylinder head with a 5/16 inch nutdriver or socket. Make sure there is no dirt ordebris on the top of the head which could falldown into the engine. Do not lose the copper

gasket which seals the glow plug. Touch theglow plug to the contacts of the glow starter.All of the coils should glow bright orange.Sometimes the first few coils will not glowwhile the rest are bright, most likely indi-cating a bad plug. Do not perform this test indirect sunlight. If the glow is dim orange, thenthe glow starter battery should be replaced orrecharged.

Tip: Glow plugs can be damaged by run-

ning the fuel mixture too lean, applyingmore than 1.5 volts to the plug, or by run-ning out of fuel while the engine is runningat high RPMs.

Replacement glow plugs are available fromyour hobby shop or Traxxas. From the factory,your engine was equipped with a standardlong-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). Glowplugs with idle bars should not be used.Always use the new gasket which comes withthe glow plug. Do not use plugs with idle bars.

Tip: Traxxas heavy-duty glow plugs (part#3231) should also be used in TRX .12sequipped with tuned pipes. Do not use theheavy-duty plug in a TRX .12 with stockexhaust or poor performance may result.


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FUEL PROBLEMS

A clean, properly-lubed, air filter is essentialfor maintaining the performance of the engine.NEVER RUN YOUR ENGINE WITH A DRYFILTER, OR WITHOUT THE AIR FILTER INPLACE. If dirt gets into the engine, all of theinternal parts can be severely damaged in ashort amount of time. INSPECT THE AIR FIL-TER EACH TIME YOU REFUEL. The air filtercould become saturated with fuel when themodel is turned upside down, or when theengine is flooded. The air filter should becleaned at the first sign of deterioration, oilcontamination, or blockage.

If you will be running your engine inextremely dusty conditions or where there isfine, powdery dust, then the Traxxas two-stageoil/foam air filter (part #4062)or three stage fil-ter (part #4063) should be used.

Your engine consumes more fuel than youmight expect. It will run approximately 8-10minutes on a tank of fuel. Run time will beeven less during break-in because of the richfuel mixtures. Try not to let the fuel level dropbelow 1/4 of 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 fuelpickup point in the bottom of the tank. The airin the line causes erratic performance and rad-ical leaning of the fuel mixture. In this case, theengine may lean out, stall, and the glow plugcould be damaged.

The main component of model engine fuelis methanol. Methanol will attract moisturefrom the air when left uncapped. If the fuel isleft uncapped, for even a few days, it

should be disposed of. Also, fuel left openwill get dust in it, which can damage yourengine. Keep the fuel tightly capped at alltimes and store it away from direct sun-light.

Poor quality fuels may lead to overheatingproblems. If the methanol is not pure, or thenitro content is composed of nitromethane andnitropropane instead of nitromethane, youcould experience all types of running problems

in addition to destructive ash buildup insidethe engine. Also, if the fuel does not containboth castor oil and high quality synthetic oil,then the fuel will cause many problems andshould not be used. You simply MUST use afuel which meets the standards outlined in thefuel requirements section of this manual.Other types of fuel are unacceptable.

The TRX engine is designed to performbest on nitro contents between 10 and 20%.

When the 20% mark is surpassed, all risk andresponsibility for engine performancebecomes your own. Engine temperatures willincrease when more nitro is used, with onlymodest gains in performance, and a decreasein engine life. Use less nitro in warm weath-er, and more in cool weather. Perform thefollowing test to determine if you are usingenough nitro. Start the engine, allow it to warmup, and disconnect the glow starter. If there isno discernable drop in RPMs, then you areusing enough nitro. If the engine doesnt idlesmoothly or as fast when the glow starter isremoved, then the next higher level of nitroshould probably be purchased on your nextgallon of fuel. This test assumes that the glowplug is good (a bad glow plug will also causepoor running when the glow starter isremoved) and the engine is broken in.

It is possible for the fuel lines to developcuts and pinhole leaks when the fuel linesare removed from their fittings. These leaksallow air in the line which interrupts the fuelflow. If a leak is suspected, replace the lineswith new tubing. DO NOT BLOW ON THETUBES WITH YOUR MOUTH. MODEL FUELIS POISONOUS.

FLOODING:

Occasionally, you may accidentally floodthe engine. Symptoms of a flooded engineinclude difficulty pulling the starter and muffledsound coming from the exhaust. Remove theglow plug with a 5/16 inch nut driver and thenremove the air cleaner. Turn the engine upsidedown to drain any excess fuel out of the com-bustion chamber and carburetor. Pull the recoilstarter 4-5 times to clear the engine. Beextremely careful not to let the fuel spray intoyour face!Turn the model back over, install theglow plug, and re-prime the carburetor. Theengine should start and run normally.

CARBURETOR TIPS:

The carburetor, because of its simpledesign, is very reliable. Its only enemy is dirt.Dirt particles become embedded in the needleseats and prevent consistent mixture settings.

The carburetor should be suspected when asudden and persistent leaning of the fuel mix-ture is observed (the engine may suddenlyspeed up). To dislodge the dirt particle, tryscrewing the high and low-speed mixturescrews all the way in and then back out to theiroriginal settings. If the engine doesnt return tonormal operation, try backing the mixturescrews out several more turns and then usethe prime button to force fuel through the car-buretor. Return the mixture screws to their


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original position. The engine will be floodedafter this process so follow the steps in theabove paragraph to return the engine to nor-mal. If the dirt particles are still not cleared,then remove the carburetor and clean both thehigh-speed and low-speed needles with dena-tured alcohol. To prevent this from re-occur-ring, replace the air filter with a new unit andinstall a new in-line fuel filter between the car-buretor and fuel tank.

FUEL MIXTURE TIPS:

The fuel mixture is the largest variable youhave to control while operating your engine.Fuel brand, ambient temperature, and humidi-ty all effect how your mixture should be set. Ifthe engine runs great one day but runs rich orlean on another day, it is most likely the resultof a change in the air quality and temperature.This should be expected and adjusted for.

STARTER PROBLEMS

Most starter problems result from pullingthe starter too far or after the engine has beenflooded and/or is in a locked condition. Thestarter can be removed from the engine byremoving the four 3x6mm philips head screws

that fasten the housing to the engine. Thestarter must be removed in order to performany service on it. Refer to rebuild steps 6-12on pages 13-14 for starter service.

COOLING PROBLEMS

Engine overheating is most often caused byrunning the engine too lean or because thecooling air for the cylinder head is blocked. Ifthe mixture is too lean, simply allow the engine

to cool, richen the mixture, and try again (boththe high-speed and low-speed mixtures havean effect on running temperatures). Truck,buggy, and car bodies must have holes cut inthem to allow cooling air to move across the finsurfaces of the cylinder head. On some bodies,the windshield should be cut out so that aircan flow to the head. Additional cooling can beachieved by cutting an opening in the back ofthe body so that air will pass completelythrough the body.

If the fuel meets all of the requirements, themixture is set rich, the head is receiving ade-quate ventilation, and the engine continues tooverheat, then the model may have a bound-up drivetrain. Look for dirty wheel bushingswhich may have tightened or any other movingpart which may be causing excess drag on themodel. Driving through deep sand and grasswill also put excessive loads on the engine.

CHANGING CLUTCH BELLS

The clutch bell gear will wear from use andshould be changed periodically. The gearshould be replaced when the teeth on the gearare sharp and pointed rather than square-shouldered. Metal particles become embeddedin the spur gear and it should be replaced atthis time also. Refer to engine rebuild stepsand the exploded-view drawing when disas-sembling the clutch mechanism (the numbersin parenthesis are part identification numbers).

MAINTENANCE

CONNECTING ROD

The connecting rod inside the engine

should be inspected for wear about every gallonof fuel.We recommend that the connecting rodbe replaced if it shows wear. See enginerebuild steps 1-5. If your engine is being usedin an application that requires continuoushigh-speed operation, or if a lean fuel mixturehas been used to gain performance, then theconnecting rod should be checked more often.Follow the step-by-step instructions in therebuild section of this manual to inspect orchange the connecting rod. Failure to inspect

the connecting rod at the prescribed intervalscould result in severe internal engine damage.

AIR CLEANER

The air cleaner is essential for keeping dirtout of the engine. The air cleaner should beinspected carefully every time you refuel. Itshould be cleaned and re-oiled whenever it isdirty. If you will be running your engine inextremely dusty conditions or where there is

fine, powdery dust, then the Traxxas two-stageoil/foam air filter (part #4062)or three stagefilter (part #4063) should be used.

CLEANING

The engine should be kept clean of oil andgrime for more effective cooling. The moreoften the engine is cleaned, the easier it will beto clean the engine. The easiest and mosteffective cleaning method is to use dena-

tured alcohol applied with a trigger spraybottle. Denatured alcohol is available frompaint and hardware stores and it will not attackthe plastics used in the construction of yourmodel. THE DENATURED ALCOHOL ISFLAMMABLE SO KEEP IT AWAY FROMOPEN SPARKS AND FLAME. FOLLOW ALLOF THE PRECAUTIONS ON THE CONTAIN-ER. Remove the batteries and radio systemfrom your model before spraying it with the


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cleaner. Tilt the model up so that the alcoholwill dissolve the grime causing it to run off theback of the model. The alcohol will then evap-orate leaving little residue.

STORING YOUR MODEL

Use an after-run product in the enginewhenever the model is going to be stored andwhenever it has been cleaned with alcohol.Use of the after run oil is described on page 7.The denatured alcohol and the alcohol in thefuel attracts moisture so the oil is needed toprevent rusting and corrosion. Clean themodel as thoroughly as possible. Clean and oilthe bushings in the front wheels and rearaxles. Store unused fuel in a tightly-cappedcontainer away from direct sunlight.

PRECAUTIONS

If the precautions are followed and your modelis 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 safeand responsible manner could result in prop-erty damage and injury.You alone must see toit that the instructions are followed and that theprecautions 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 youngchild. Keep it out of childrens reach.

* The fuel is flammable Do not allow sparks,flame, or smoking in the presence of modelfuel.

* The engine emits poisonous carbon monox-

ide gas just like a real automobile engine.Always run the model in a well-ventilatedarea. Never attempt to run the engine indoorsunless there is adequate ventilation.

* The engine, head, and exhaust systembecome extremely hot during use. Be carefulnot to touch these parts, especially when re-fueling or reaching for the starter handle.

* Do not drive the model at night, on publicstreets, or in large crowds of people.

* Do not reach underneath a running model to

pick it up. You might accidentally come incontact with the spinning flywheel.* Fuel-powered models are very fast and can

cause injury if allowed to run into people oranimals. For this reason, it is very importantto maintain the mechanical integrity of themodel. The radio system, batteries, connec-tions, and brakes should all be kept in goodworking 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 latein the evening. Try to find a place to run yourmodel where no one will be disturbed by itsnoise.

MECHANICAL PRECAUTIONS

* The engine is capable of turning 30,000 ormore RPMs at full throttle. Continuous full-throttle, high-speed operation will rapidlydecrease the life span of the internalengine parts. For longer engine life, varyyour speed. If the engine will be run athigh speeds in a racing situation, expectto replace worn parts more often.

* Do not attempt to operate the engine usinggasoline, alcohol, naptha, or any other fuelother 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 timeyou re-fuel. Replace the air cleaner wheneven the slightest signs of deterioration arevisible.

* 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 thechange.

* Do not over-rev the engine. The engine willover-rev if the throttle is fully opened whilethe rear wheels of the model are off theground.

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

* Do not allow the engine to run out of fuelwhile it is running at high RPMs. This coulddamage the glow plug.

* Test the radio system each time before youoperate 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 ordeep sand. This puts excessive loads on theengine and could cause it to overheat.

* Do not run your car, truck, or buggy throughwater. 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 outmore than 12 inches. Longer pulls are notnecessary and can damage the starter.

* Using fuels containing more than 20%nitromethane will cause the engine to runhotter and decrease its longevity.


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MORE ABOUT FUELS

Do not use fuels blended with 100% syn-thetic oils, without castor. Synthetic oils havea lower flash point than castor. Thus, whenthe engine reaches its higher operating tem-peratures, the synthetic oil may burn off thebearing surfaces and not provide adequatelubrication. This will result in severe damageto your engine. When castor oil is present infuel, 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 oilwill cause varnish to build up inside theengine. The varnish coats the parts and pre-vents effective heat transfer.

The purpose of the nitromethane in the fuelis to increase the amount of fuel being burned,thus improving power. The TRX-12 engine willrun on fuels which contain no nitromethane;However, fuels containing 10-20%nitromethane should be used. Increasing thenitro content beyond 20% may improve powerup to a point; however, running temperatureswill 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 inmodel engines. Nitroethane and nitropropanecause the engines to run very hot, but aresometimes used in small percentages to lowerthe cost of the fuel. Nitropropane is a knowncarcinogen, 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 lifeand performance of your engine. Not all fuel iscreated equal. If there is any doubt about thecontent of the fuel, the quality of the fuel, orthe reputation of the maker or seller, do notbuy it. Your best source for fuel is a reputable,

well-known hobby dealer who has experiencewith small model engines. Always read the thelabel, but generally speaking, nationally-rec-ognized, brand-name fuels should have the oilcontent 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 duringbreak in and then switch to a higher nitro per-centage for normal running.


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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 isfully opened from idle

Engine stalls while driving around turns

Engine stalls while running for noapparent 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 ............................Excessive nitro 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 ................

Glow plug 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 tankReplace fuelPrime carburetorCharge glow starterReplace glow plug- see Glow PlugProblems sectionSee Fuel Problems-Flooding sectionAllow engine to cool- find cause for overheatingReadjust carburetorRemove and clean exhaust system

Clean air filter

Turn flywheel by hand to retract starter rope-problem will correct itself after first runRepair starter- see Starter Problems sectionRepair starter- see Starter Problems section

Clear excess fuel- see Flooding sectionRepair starter- see Starter Problems sectionDisassemble engine to find cause

Increase idle speedUse prime button to force bubble through-check for a hole in the fuel lines

Replace glow plug- see Glow PlugProblems sectionAllow engine to cool- find cause for overheatingReplace pressure hose- Clear blockage atexhaust header fitting- check flow to andfrom tank

Set high-speed mixture to a leaner settingCheck glow plug gasket/ tighten glow plugReplace glow plug- see Glow Plugproblems sectionReplace fuelClean carburetor- see Fuel Problems sectionStop at once- find cause for overheating

Tighten slipper clutch (when equipped)Use a lower gear ratioReplace clutch shoes (return for service)Find the bound item and repairReturn for service

Richen high-speed mixtureDirect air to the headUse fuel with lower nitro contentPurchase correct fuelPurchase correct fuelCheck for bound up drivetrainRichen low-speed mixture

Richen high-speed mixtureLean low-speed mixtureStop at once- find cause for overheatingUse prime button to force bubble through-check for a hole in the fuel lines or low fuel levelTest and/or replace glow plug- see GlowPlug Problems sectionReplace pressure hose- Clear blockage atexhaust header fitting- check flow to andfrom tank

Replace glow plug- see Glow PlugProblems sectionRichen low-speed mixture

Lean high-speed mixture

Refill fuel tankIncrease idle speed

Replace glow plug- see Glow PlugProblems sectionStop at once- find cause for overheatingReplace fuel line- install fuel filterReplace pressure hose- Clear blockage atexhaust header fitting- check flow to andfrom tank

pro.15 manual pro-.15-manual 0

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