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Rotary Evolution · 10-27-2013, 11:24 AM

the lower screw is for idle mixture adjustments, the larger top screw is for idle speed adjustments.

adjust the top one to get near desired idle speed then for the bottom one: warm up the engine to operating temp then begin turning it clockwise until the engine idle speed raises to peak and then begins to stumble then turn it back out 1/8th of a turn. once the bottom screw is adjusted then you can set the idle speed with the upper screw.

make mixture adjustments rather slowly, if you try to go too fast you may overshoot where it should be.

if the idle is still poor then there are other issues to resolve. cleaning the metering jets in the hitachi and nikki carbs is not easy to do and sometimes plugged up jets are overlooked. vacuum leaks will also cause you to beat your head against the wall in trying to fine tune the carb.

10-27-2013, 11:24 AM	#3
Rotary Evolution rotaryevolution.net Join Date: Feb 2011 Location: Las Vegas, NV Posts: 248 Rep Power: 15	the lower screw is for idle mixture adjustments, the larger top screw is for idle speed adjustments. adjust the top one to get near desired idle speed then for the bottom one: warm up the engine to operating temp then begin turning it clockwise until the engine idle speed raises to peak and then begins to stumble then turn it back out 1/8th of a turn. once the bottom screw is adjusted then you can set the idle speed with the upper screw. make mixture adjustments rather slowly, if you try to go too fast you may overshoot where it should be. if the idle is still poor then there are other issues to resolve. cleaning the metering jets in the hitachi and nikki carbs is not easy to do and sometimes plugged up jets are overlooked. vacuum leaks will also cause you to beat your head against the wall in trying to fine tune the carb. __________________ http://rotaryevolution.net Last edited by Rotary Evolution; 10-27-2013 at 11:30 AM.