Join Date: Jun 2015
Location: West Chester, Pa.
Check you air filter for that cylinder first. As it starts to clog, the cylinder will develop a rich condition. The air mixture screws only effect the idle circuit. If you still want to try adjusting the screw, turn it in 1/4 turn at a time and try it. To check the plugs correctly, you have to have the engine warmed, run the rpms up around 4,000, then shut off the engine and hold the throttle open until the engine stops. Then you will get the best plug color. If the plugs are still black, dirty air filter or 2 big of a main jet.
Just my 0.02.
'99 VN750, all stock
performed driveshaft maintenance
checked the ACCT using the Grambo Trick
Sycned carbs with flow meter
Yuasa YTX14AHL-BS AGM Battery
NGK DPR7EIX-9 Irridium Spark Plugs