there is a leak down tester available, must like checking for a boost leak on a turbo car
hey op did you check compression? seems like maybe the rings are worn and you don't have good compression to fire the thing up at all times
leak-down testing on a two stroke is a bit difficult.there aren't any valves,the cylinder is only sealed at the top of the stroke.
bad rings are a possibility.on the crank seals,one end is generally in the transmission,so it will be pulling in oil.if the oil level in the trans keeps going low and there's a lot of oil in the exhaust,this can be the cause.
the other end of the crank has the alternator/ignition on it.remove the cover(on those where you can)and when running,spray a bit of starter fluid in.if the engine revs up,the seals are gone.