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11.
Vehicle Settings
a) Engine Fine Tuning
After the run-in stage of the engine (see chapter 8. h), you may start the fine tuning process to increase the performance.
To that effect, optimise the mixture for idle speed (and transfer to full throttle) at the idle speed mix adjustment screw
and at the main jet needle for full throttle.
This fine tuning is significantly simplified by the carburettor with the material combination aluminium/plastic used in this
vehicle. Conventional full metal carburettors become very hot in operation. This evaporates parts of the fuel in the
carburettor already. The lower heat intake of the plastic prevents this effect in the carburettor installed here.
Adjusting the main jet needle (full throttle mix)
• Start the engine and remove the glow-plug starter as usual.
• Let the engine warm up for approximately 1 min.
• Drive the model as usual.
• If the engine runs ‘too fat’, tune down the mix by twisting the main jet needle inwards by 1/16th of a turn until you
have achieved the desired setting.
• Make sure that the mix is not too thin. A slight white smoke vane should be visible from the exhaust at all times.
Performance increase by higher nitromethane share
As already described in chapter 8. i), the nitromethane share should usually not exceed 25% in racing operation.
For an even better performance, you can change to a fuel with up to 30% nitro methane. However, there is the danger
that the engine would show no satisfactory road performance any more if you return to a fuel with a lower nitro
methane share.
If you want to permanently drive with a fuel with a high nitro methane content, we also recommend replacing the
present with a thicker cylinder head gasket to reduce compression.
If you do not reduce compression, the engine may overheat and run incorrectly!
Adjusting the idle mix adjusting screw
• Start the engine and first adjust the main jet needle as described above.
• Reduce the speed until the centrifugal clutch does not engage anymore and the wheels stop turning when you take
the model off the ground.
• Leave the engine running at idle speed for approximately 10 - 15 seconds.
• While you are holding the model with your hand, drive at full throttle once briefly and strongly. Take care not to
contact moved or hot parts!
• If the engine stalls once you run at full throttle, the idle speed mix is too lean.
• Enrich the mix by unscrewing the screw by 1/16 rotations counter-clockwise while the engine is switched off.
• Restart the engine and repeat the procedure until the speed transition from idle speed to full throttle is soft and
spontaneous. A short delay in reaction is normal.
• If the engine smokes strongly during transition from idle speed to full throttle and sounds very rough, then the mix is
too fat.
Summary of Contents for REX-X 2WD RtR
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