when i spray carb cleaner at the bottom of the carb the engine by the hoses and idle screw rpms go up . with air cleaner on and with it off . but also , when i spray carb cleaner into the top of the carb itself , same thing , the engine rpms go up . should i start with changing the carb to manifold gasket ? it has one of those thick cork ? style gaskets . i tried pinching each hose with needle nose pliers , no change in rpms .