hi on my carb there is a screw with a spring which when u turn it in make the bike rev more nd wen u turn it out revs lower. there is also a screw on the airbox/carb if i screw in/out will this improve the bike performance? do these screws have anything to do with the mixture? aslo i had a black spark so if these have anythink do do with the mixture can sum 1 please tell me how to adjust thanks

1234, July 2009

The first screw is the tickover speed screw, and the second one is the idle mixture screw which should be set 1 turn out from fully in. Neither will improve the performance of your bike, no matter how they are set. A sooty spark plug is a sign of a rich mixture, so adjust the idle mixture screw and check your air filter for cleanliness.

John, July 2009