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Things You'll Need
Instructions
Locate the two needle valve thumbscrews on the engine. One needle valve is for the top end mixture and the other is for the low idle setting. Some are marked "H" for high and "L" for low. Check the engine manual for the manufacturer's specifications regarding location and marking.
Start the model glow engine. Use the appropriate voltage battery and glow plug connector clip as recommended by the engine manufacturer. If the engine stalls, make an adjustment to the low end or idle needle valve before attempting to restart the engine.
Close the idle or low end needle valve screw by turning it clockwise until it is closed, then open the valve two to three full turns counterclockwise.
Start the engine and run it at full throttle for 20 seconds, then bring it to idle for about 20 seconds. Gauge the time with a watch or clock equipped with a sweep second hand.
Squeeze the fuel line with your fingers and take note of any changes in engine speed. If the speed increases and then the motor stops, the idle speed valve is allowing too much fuel (running rich) into the engine.
Turn the idle speed needle valve 1/4 turn clockwise and restart the engine. If the speed decreases and the motor stops, not enough fuel (running lean) is being supplied and the valve needs to be turned 1/4 turn counterclockwise.
Continue adjusting the idle speed needle valve until the engine does not gain or lose speed before stopping when you squeeze the fuel line. As the low speed tuning improves, make small incremental turns of the needle valve.
Run the engine at full throttle. Make any small adjustments that may be
necessary. A well-tuned model glow engine will idle reliably and then pick up speed quickly and cleanly when the throttle is fully opened.