well if its stuck then you broke sumptin! first undo the carbs and reed cages, then look through with a flash light, see if the piston is broke. if both look ok then take off the stator cover and make sure the flywheel didn't loose a magnet and jam up. lastly, this being the pain in the ass side of things, take off the clutch cover and inspect the idler gear, and kick starting shaft. anything else in there should be very obvious.