[Classic]

The breather is just a rubber tube that runs from the lower front of the front just to the back of the right side air intake backplate. If you disconnect it from the backplate, remove the oil filler cap, I think you ought to be able to blow through it with not a whole lot of resistance. I think. I never heard of overfilling causing any kind of blockage like you describe but it would make a mess of the right side air intake and gunk up the carb really nicely but it would have to be grossly overfilled. Cam plugs can leak on these bikes it's more common on the older ones but the cam plug on the front jug is on the opposite side of the engine.