8. Setup
a) Engine fine tuning
After the run-in phase of the engine, you can start the fine tuning to increase the performance. To that effect, optimize the mix preparation for idle speed and
change-over at the idle speed mix adjusting screw and at full throttle on the main nozzle needle.
This fine tuning is significantly simplified thanks to the carburettor with the material combination aluminium/plastic. Full-metal carburettors become very hot
during operation. As a result, parts of the fuel already evaporate in the carburettor.
The carburettor setting selected while the engine is cold therefore does not remain constant during operation. The low heat absorption of the plastic prevents this
effect.
Adjusting the main nozzle needle (full throttle mix)
• Start the engine and remove the glow-plug starter.
• 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 nozzle needle inwards by 1/16th of a turn until you have achieved the desired setting.
• Make sure that the mix is not too lean. A light white trail of smoke should always be visible coming out of the exhaust pipe.
For an even increased performance, you can change to a fuel with up to 30% nitromethane. 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 nitromethane share.
If you permanently want to drive with a fuel with a high nitromethane content, we also recommend replacing the present with a thicker cylinder head
gasket to reduce compression.
If you do not reduce the compression, an overheating of the engine and faulty run can be the consequences
Adjusting the idle speed mix adjusting screw
• Start the engine and adjust the main nozzle needle as described.
• Reduce the speed until the centrifugal clutch does not engage any more and the wheels do not turn any more when lifting the model off the ground.
• Leave the engine running in idle speed for approximately 10 – 15 seconds.
• While you are holding the model with your hand, drive at full throttle once briefly and strongly.
Make sure not to touch moving parts!
• If the engine stalls as soon as you run at full throttle, then the idle speed mix is too lean.
• Enrich the mix by unscrewing the screw by 1/16 rotations 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 small delay in response 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.
• Make the mix leaner by screwing in the screw by 1/16 rotations 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 small delay in response is
normal.
• Drive the model as usual in order to get a feeling of how the engine reacts to load changes.
• Modify the setting until the performance characteristics correspond to your expectations.
Once you have carried out these settings, a readjustment of the throttle stop is however necessary.
Adjustment of the throttle stop screw (idle speed-adjusting screw)
The idle speed adjusting screw regulates the idle speed via the position of the slide carburettor (the throttle stop).
• The higher the carburettor throughput, the higher the rotation speed.
• Turning the adjusting screw clockwise increases the throughput.
• Turning anti-clockwise lets the slider retract further and thus reduces the gap.
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