can you move the gov lever to close the throttle? if not, internal gov assembly is most likely problem. If the engine went into an overspeed sometimes the fly weights push out and become stuck. that is a possibility. Only way to inspect without splitting sump from block would be to use a mini camera. I always used one for cylinder inspection, transmission, etc. They are not difficult to split, just remove and flip over. remove sump and look at it. Will need new gasket, may as well replace seal too.