you dont want any exhaust leaks ! thats not good , what color was the plugs?
not the pistons, you have to pull the cable into the full open position and pull over the
engine . to test the oiler . you need to be VERY DILIGENT about cleaning the crankcase
out of ALL the debris , last one i did i sat there for over an hour spraying clean solvent into the engine and sucking it back out, have the cylinders bored get new pistons and
rings , then mix your oil in the gas tank . for the first tank, put a mark on the oil reservour and make sure it is using oil from the tank, you might foul a plug but thats cheaper than a rebuild , no oil could seeze the bottom end , so it could have just been jetted wrong for the elevation/temperature you were riding it at .