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Briggs carb jet adjustment

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What is the correct procedure for adjusting the metering jet in the bottom of the fuel bowl on a Briggs I/C 12hp vertical shaft engine? I have it running good, but I want to make sure that I am not going to be dumping excessive gasoline into the cylinder, thus contaminating the engine oil.


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I've never heard that gas could get in the oil, at least due to a main jet setting. If my memory serves me, for my Briggs 8hp, the Briggs service manual instructs to use a tachometer and set the engine speed to 3500 rpm (max governed rpm), then open the main jet until the engine RPM begins to drop. Note the screw position, then close the main jet, past peak RPM until the engine RPM begins to drop again. Note screw postion, then adjust the screw postition midway between the two noted positions. Then, if you also have a low speed mixture screw, repeat the process at idle with the low speed mixture screw. As a final check, hold the governer at idle, set the throttle to max, then let go of the governer and note if the engine speed accelerates smoothly. If not, the high speed mixture needs to be tweeked, and think it was towards lean, but I'm not positive about that. But to be honest, I don't think you need to make any adjustments if it's running fine.


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