Gary,

Thats kinda what I've been thinking too. Maybe inject some afterrun oil into the breather, flip the prop over a dozen times and clamp off the breather hose. Might be best to clamp when the piston is at bottom dead center. At that time the crankcase volume would be the least.

I don't think applying afterrun oil into the carb throat will get a good quantity into the crankcase. The oil would have to run past the piston and ring then into the crankcase. Unlike a 2 stroke where the oil enters the crankcase first.

Seems the worst rust on my 100 was in the rear bearing and counterweigth on the crank... closest to the breather hole.

Tom...