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NITRO RUSTLER • 29

ThE TRx 2.5 RacING ENGINE

Fine-Tuning the Carburetor

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

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

Tuning the Engine by Temperature

The following procedures require an 
optional infrared temperature probe or  
on-board temperature gauge (Traxxas  
on-board digital temperature gauge, 
part #4091). Engine temperature can 
be used as an effective tuning aid 
when you understand the relationship 
between engine temperature and ambient temperature. The engine 
operating temperature, when tuned for maximum performance, will 
vary according to atmospheric conditions, engine load, gauge accuracy, 
and many other factors. The atmospheric condition that has the most 
influence on engine temperature is air temperature. Expect the engine 
temperature to vary almost in direct proportion to air temperature. 
Assuming you tuned the engine for the same maximum performance 
each day, the engine will run about twenty degrees hotter when it’s 
ninety degrees outside than it would in seventy-degree weather. For 
this reason, we cannot give you a definitive temperature range that 
indicates the best possible engine tuning.

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

Once the engine is tuned, then observe the temperature.

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

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

any

 signs of overheating.  Richen the fuel mixture slightly to provide 

a safety margin of additional cooling lubrication. Symptoms of 
overheating include:
• Steam or smoke coming from the engine (not exhaust)
• Hesitation or stalling during acceleration
• Popping or clattering sound when decelerating (detonation)
• Fluctuating idle speed

Summary of Contents for 44094-1 Nitro Rustler

Page 1: ...owner s manual MODEL 44094 ...

Page 2: ...ed and proven to produce the best performing engine possible Using traditional or old fashioned procedures could reduce engine performance and longevity 3 Before You Proceed 4 Safety Precautions 5 Tools Supplies and Required Equipment 6 Anatomy of the Nitro Rustler 7 Quick Start Getting Up to Speed 8 Traxxas TQ 2 4GHz Radio System 14 The TRX 2 5 Racing Engine 30 Driving Your Model 31 Tuning Adjust...

Page 3: ...s and helpful hints identified by the icons below Be sure to read them An important warning about personal safety or avoiding damage to your model and related components Special advice from Traxxas to make things easier and more fun Refers you to a page with a related topic Support If you have any questions about your model or its operation call the Traxxas Technical Support Line toll free at 1 88...

Page 4: ...gin in all directions around your model to prevent collisions The engine can be loud If the noise makes you uncomfortable wear ear protection Be considerate of your neighbors by not running your model early in the morning or late in the evening Do not kink the antenna wire Kinks in the antenna wire will reduce range Do not cut the antenna stinger or any other part of the antenna wire Cutting the a...

Page 5: ...uel see page 18 Small flat blade screwdriver for tuning 1 8 inch blade After run oil to protect the engine from corrosion NiMH 7 2V battery pack 10 quart 5010 20 quart 5020 33 quart 5030 10 gallon 5060 20 gallon 5070 33 gallon 5080 Glow plug and wheel nut wrench 4 way wrench Foam air filter oil see page 19 U joint wrench 1 5mm L wrench 2 0mm L wrench Turnbuckle wrenches NiMH battery charger Afterm...

Page 6: ...hock Oil Damper Tie Rod Turnbuckle Throttle Brake Servo Transmission Air Filter Pipe Header Engine see pg 14 for details Pressure Line Fuel Line EZ Start Motor EZ Start Plug Shock Tower Body Mount Spur Gear Chassis lower Slipper Clutch Half Shaft On Off Switch Receiver Antenna Mount Pipe Hanger Tie Bar Bulkhead Front Camber Link Turnbuckle Chassis upper ...

Page 7: ...cedure for your TRX 2 5 5 Install batteries in the transmitter See page 10 14 Break in your engine See pages 24 26 Nitro Rustler requires 4 AA alkaline or rechargeable batteries for the transmitter Follow the break in instructions exactly to ensure the best performing longest lasting engine 6 Install batteries in the model See page 10 15 Tune your engine See page 27 The Nitro Rustler requires 4 AA...

Page 8: ...n that the servos seek when the transmitter controls are at the neutral setting NiCad Abbreviation for nickel cadmium The original rechargeable hobby pack NiCad batteries have very high current handling high capacity and can last up to 1000 charging cycles Good charging procedures are required to reduce the possibility of developing a memory effect and shortened run times NiMH Abbreviation for nic...

Page 9: ...vo Channel 2 Throttle Servo TQ 2 4GHz Transmitter Steering Trim Throttle Trigger Steering Wheel Power Switch Battery Compartment Set Button Red Green Status LED TRAXXAS TQ 2 4GHz RADIO SYSTEM Applying The Decals The main decals for your model have been applied at the factory Additional decals are printed on self adhesive clear mylar and are die cut for easy removal Use a hobby knife to lift the co...

Page 10: ...power indicator light does not indicate the charge level of the battery pack installed in the model Refer to the LED Codes section on page 13 for more information on the transmitter s status LED codes RADIO SYSTEM RULES Always turn your TQ 2 4GHz transmitter on first and off last This procedure will help to prevent your model from receiving stray signals from another transmitter or other source an...

Page 11: ...model turns left Channel 1 would need to be reversed to correct the servo direction Use the following procedures to reverse the steering or throttle channel if necessary Servo reversing should only be required if you accidentally reset the direction of a channel Do not reverse the throttle or steering channels unless necessary Note Before performing these procedures make sure that both the transmi...

Page 12: ...e hand held transmitter Range Testing the Radio System Before each running session with your model you should range test your radio system to ensure that it operates properly 1 Turn on the radio system and check its operation as described in the previous section 2 Have a friend hold the model with the engine off 3 Walk away from the model with the transmitter until you reach the farthest distance ...

Page 13: ...tion Fail Safe Your Traxxas radio system is equipped with a built in fail safe function that returns the throttle to its last saved neutral position in the event of a signal loss The LED on the transmitter and the receiver will rapidly flash red when the fail safe mode is activated If Fail Safe activates while you are operating your model determine the reason for signal loss and resolve the proble...

Page 14: ...ne break in will take between one and two hours Old style break in procedures such as idling the engine on the bench for several tanks of fuel or simply running the engine with a very rich fuel mixture for the first 4 tanks of fuel will not achieve the best results Follow the easy steps in this manual AIR FILTER MAINTENANCE A clean air filter is critical for long engine life Due to the high perfor...

Page 15: ... Head Cylinder head EZ Start Motor Low Speed Needle Throttle Arm Clutch Bell Flywheel Carburetor Air Intake Fuel Intake High Speed Needle Idle Speed Adjustment Screw EZ Start Plug Positive Wire Negative Wire Fuel Line Fuel Tank Tuned Pipe Exhaust Tip Pressure Line Ground Wire Glow Plug Wire Crankshaft Crankcase EZ Start Drive Unit ...

Page 16: ...ure inside the crankcase Crankcase The engine s body that contains all of the running mechanical components Crankshaft The main shaft of the engine that holds the reciprocating assembly Cooling fins The cooling fins are milled into the cylinder head and crankcase and cause heat to be drawn away from the engine Heat is removed when it dissipates into the air passing across the cooling fins It is im...

Page 17: ...onnecting rod and moves up and down in the cylinder sleeve The precise fit between the piston and the sleeve creates a seal that allows the engine to have the required compression for combustion Port Ports are openings in the sleeve that allow atomized fuel to enter the combustion chamber and burned exhaust gases to exit The shape and location of the ports are a large factor in controlling the eng...

Page 18: ...mps more power and a smooth throttle response For those who want to run higher nitro 33 Top Fuel is the optimum nitro percentage for the TRX 2 5 Racing Engine Increasing the nitro beyond 33 can introduce the need for engine modifications ports head shimming etc to avoid starting and tuning difficulties There are limits to how much nitro an engine can effectively use to make more power Lower nitro ...

Page 19: ...d dirt constantly move through the filter anytime the engine is running Even if you can t see dirt on the filter it is present inside the foam after any amount of run time If you exceed the recommended cleaning intervals your engine will be damaged Engine damage or wear due to dirt ingestion is easy to detect and one of the top causes of premature engine failure Air Filter Cleaning Instructions 1 ...

Page 20: ...to meter the fuel and maintain the ideal air fuel ratio in these ever changing conditions For example colder air is more dense more air molecules for a given volume of air and therefore requires more fuel more fuel molecules to maintain the correct air fuel ratio Warmer air is less dense fewer air molecules and therefore needs less fuel to maintain the correct air fuel ratio The tuning needles are...

Page 21: ...o not re adjust your carburetor from the factory settings until after the engine is started and running and you have been able to observe the engine running to assess what minor adjustments may be required to compensate for fuel temperature and altitude Adjustments are usually made in 1 8 or 1 16 turn increments If the engine sticks at TDC see page 35 for instructions on freeing the engine The Idl...

Page 22: ... LED indicates the status of the EZ Start electric starter motor The cush drive mechanism in the drive unit prevents damage to the gears caused by engine kickback SmartStart protectioncircuitrypreventsdamagetothemotorbycutting poweriftheloadonthemotororotherelectronicsexceedssafelimits Charging the EZ Start Battery The included charger can be used to charge the included battery pack The battery pa...

Page 23: ...ion circuit to shut off the power to the motor Allow at least three minutes for the starter motor to cool and the circuit to automatically reset before continuing Use the time to find and eliminate the condition that caused the excessive load on the starter motor Use a Strong Starter Battery A weak starter battery or one that has not been fully charged may not deliver enough power to crank the eng...

Page 24: ...braking could cause the engine to stall unnecessarily Special break in fuels are not recommended Use the same fuel you plan to use everyday If possible avoid breaking in the engine on extremely hot or cold days see page 26 Pay careful attention to the fuel level Do not allow the fuel tank to run completely empty An extremely low fuel level causes the mixture to run too lean This could result in a ...

Page 25: ...d may increase and cause the model to try to creep forward when stopped Reduce the idle speed by turning the idle speed adjustment screw see page 15 on the carburetor counterclockwise 3 When the fuel tank is nearly empty shut off the engine and refuel From here on you do not need to let the engine cool between tanks Tank 4 1 Driving procedure Gently pull the throttle trigger to full throttle over ...

Page 26: ...n sleeve to wear prematurely Wrap the cooling head with a paper towel clean rag or sock to help keep the engine running around the recommended 200 to 215 F break in temp If too much heat is contained the engine can actually run too hot Make sure that you monitor the engine s temp closely for the first couple of tanks until you get the right amount of cover for the cooling head This will of course ...

Page 27: ...ing gradually lean the high speed fuel mixture in 1 16 turn increments Make several high speed passes after each adjustment to clear out the engine and note any change in performance The TRX 2 5 is extremely powerful Remember to apply the throttle gradually to prevent wheelies or loss of control Continue this procedure until there is no longer any performance improvement If any one of the followin...

Page 28: ...he idle speed adjustment screw to control engine idle 1 When the throttle servo is in its neutral position the throttle slide should be stopped against the idle speed adjustment screw 2 Turn the screw counterclockwise to reduce the idle speed or clockwise to increase it The idle speed should be set as low as possible while still maintaining reliable running characteristics When adjusting the low s...

Page 29: ... in seventy degree weather For this reason we cannot give you a definitive temperature range that indicates the best possible engine tuning There is NO optimal temperature that can be used as a target to deliver the best engine tuning Do not rely on a temp gauge alone to tune your engine Tune the engine by paying very close attention to how it responds to changes in fuel mixture more smoke less sm...

Page 30: ...ng distances This could cause the engine to build up enough speed to exceed maximum safe rpm limits Don t drive your Nitro Rustler with drivetrain damage of any kind The engine could be damaged due to overloads on the engine caused by drivetrain friction or over revving caused by loose or missing parts Don t tow anything with your Nitro Rustler The engine is cooled by airflow created by speed Towi...

Page 31: ...each front wheel Use the turnbuckles to adjust the alignment Adjusting the Camber The camber angle of both the front and rear wheels can be adjusted with the camber rods upper turnbuckles Use a square or right angle triangle to set the camber accurately Adjust the front wheels to 0 of camber wheel perpendicular to the ground In the rear adjust the wheels to 1 to 2 of negative camber These adjustme...

Page 32: ... sleeve should be replaced when they no longer seal effectively loss of compression Symptoms include the engine being difficult to start when warm stalling when warm and stalling when throttle is suddenly closed to idle Replace the wrist pin and G clip whenever the piston and sleeve are replaced Connecting rod The connecting rod should be replaced when the piston and sleeve are replaced or after t...

Page 33: ...tions 6 Place a rag or paper towel over the engine to catch any WD 40 or after run oil that may come out of the carburetor or glow plug hole 7 Connect the EZ Start controller to the model and spin the engine for 10 seconds 8 Remove the rag or paper towel and repeat steps 5 7 two more times 9 Clean and re oil the air filter so it will be ready for use next time See page 19 for air filter maintenanc...

Page 34: ...protection mode Allow the controller to cool for at least three minutes The circuitry should automatically reset Check to make sure the wires are connected to the EZ Start motor in the Nitro Rustler The red wire should connect to the positive motor terminal indicated by a red dot next to the terminal The engine could be flooded If too much fuel accumulates in the combustion chamber at start up the...

Page 35: ...driveline that would cause excessive loads on the engine Clearing a Flooded Engine If the engine is primed for too long during startup then it can become flooded with fuel When the engine is flooded it will no longer turn due to excess fuel in the combustion chamber preventing upward movement of the piston Use the following procedure to clear a flooded engine 1 Remove the blue glow plug wire 2 Rem...

Page 36: ...1100 Klein Road Plano Texas 75074 1 888 TRAXXAS 121130 KC1797 R01 owner s manual ...

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