rich will burble lean will hesitate then quit engine should idle smoothly and return to idle after throttle snap. If engine continues to rev after idle snap it is too lean richen the l/s needle if engine bogs and burbles after snap it is too rich on bottom. If engine idles but won't rev has lots of smoke and burbles it is rich on high speed needle if hesitates and revs to a screaming pich it is lean may even stall just quick pointers I recoomend getting someone with experience to help you at local track or hobby shop.