Take the sparkplugs out...with ignition off...spin the engine over with a electric starter. Notice if the reed vales are working. Even with the sparkplugs out there should be some crankase compression. This with the reed valves working and sealing correctly ...this pumps the air fuel mix to the cylinders. Have somebody vary the throttle setting (and choke opening)while you crank it over. Tell us what you notice. Capt,n