the crank seal wont make it easy to kick over, but guess youll see when you tear it apart, its easy just take off the gas tank and pipe, then take the 4 nuts off around the base of the cylender unhook the carb and sparkplug wire n pull it off, then once on the ground take the head bolts off
it can all be connected. his crank seal went, he burnt alot of the wrong type of oil, causing damage to his rings or piston with = lowered compression.
after typing that, i just thought about it sucking in air. therres the vent tube on the case, it could have blew the crank seal, burnt a bunch of transmision oil, at the same time sucking air causing it to lean out and burn up the rings/piston.
sh*ty day dude. atleast you have an idea of whats up.