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Old 12-06-2003, 10:57 PM   #16
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Adjust needle settings - before putting the car on the track


Once the engine is running and has come up to operating temperature (within 15-20 seconds) proceed as follows:




Stage 1: Setting the main needle just a little rich
Take the car off the ground, and open the throttle fully. The engine should run cleanly until it reaches 80% of top RPM, after which it should start to run slightly rich (4-stroking):

If the engine runs cleanly all the way up to top RPM, richen the main needle (counter-clockwise) until it starts to 4-stroke at approximately 80% of its top RPM

If the engine runs too rich (4-stroking all the way) lean the main needle (clockwise) until it only starts to 4-stroke at approximately 80% of its top RPM




Stage 2: Setting the idle speed
Take the car off the ground, and open the throttle fully for 2-3 seconds. Close the carburetor and check the idle speed that occurs immediately after.

If the engine stops almost immediately, turn the idle adjustment screw clockwise to increase the idle RPM.

If the idle RPM is too high, turn the idle adjustment screw counter-clockwise to reduce the idle RPM.




Stage 3: Setting the low speed needle
Open the carburetor for 2-3 seconds and let the engine clean out. Close the carburetor and let the engine idle.

If the engine idles for 2-5 seconds and then the idle RPM decreases, the engine is running too rich during idle. Lean the low speed needle (clockwise) to remedy this condition. Repeat this step until the engine idles reliably at a constant RPM for at least 20-30 seconds after the carburetor has been opened for 2-3 seconds.

If the engine idles for 2-5 seconds and then the idle RPM increases, the engine is running too lean during idle. Richen the low speed needle (counter-clockwise) to remedy this situation.

If the engine will not idle at all, rich the low speed needle (counter-clockwise), or turn the idle adjustment screw clockwise to increase the idle RPM.






NOTE: Because adjusting the low speed needle affects the idle RPM, use the idle adjustment screw to get the engine to idle at the right RPM.




Once you are satisfied that you have achieved reliable carburetor settings, you are ready to put you car on the track.
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Old 12-06-2003, 10:59 PM   #17
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Default adjusting at track

Adjusting needle settings at the track


You can only fine-tune the main needle setting at the track. Initially, the main needle should still be set a little rich. Fill the fuel tank, run the car up to maximum speed for a few laps, and check if it reaches top RPM without running rich towards the end (4-stroking). Lean the main needle by small increments (1/12 of a turn, like 1 hour on a clock) and run the car again. Repeat these small adjustments until the engine accelerates well and reaches maximum speed without running rich. It is advised to then richen the main needle 1/8 of a turn (counter-clockwise).





Running the engine too lean will cause the engine to overheat, resulting in excessive engine wear and possibly breakdown. A fast, simple way to check the engine temperature is to apply a few drops of water to the cylinder head. The drops should evaporate only after 3-5 seconds. If they evaporate immediately the engine is too hot; richen the main needle 1/8 of a turn (counter-clockwise). Check engine temperature regularly and often.





The idle RPM and low speed needle settings may require a little fine tuning after the main needle has been set properly (see stages 2 and 3). Once properly adjusted, the engine should produce a strong, high-pitched sound at maximum speed, and a thin trail of smoke should be visible from the exhaust tailpipe.





NOTE: The carburetor settings may change with changes in weather conditions, fuel, glowplug or exhaust system. After changing any of these, always richen the main needle (counter-clockwise) to a turn and then re-adjust the main needle again on the track.
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