Perhaps you have an air leak. Check the intake side. Check the carburator bolts are tight. Check your intake manifold is not warped or cracked. Set your needles to factory settings l==1 1/4 h=1 1/2. Vent the tank. Check your fuel pick up is not cloged. Check your carbs breather is not cloged. Your carbs breather is right behind your air filter,on the front of the carb there is a small metal plate with two small screws.ddm sell a filter for it part #av 493, you can look it up.Check your plug and make shure you did not flood the engine.Check your head gasket.Hope this helps.