Does any one know how much or a easy way to find out how much to turn the fuel mixture screw. it has a stock carb. with a 128 jet size, complete aftermarket exhaust. spark plugs are fouling.

 

If you're fouling plugs,you are too rich on the main, or your float is too high,and you are putting too much fuel in the intake. Setting the mixture screw is pretty easy, just set it at 2.5 turns from seated to start, then run it until it is good and hot. Run it in 3rd gear, get up to speed, then let off the throttle,don't pull in the clutch. If you pop in the exhaust while decelerating, turn the screw out 1/4 turn at a time until it stops, and you are set. If it doesn't pop, turn in until it does, then back off until it stops.