Originally Posted by
scratchbuilder46
Bearings are good. I think the front seal has gone bad. I swapped out another .61 I have and will check to see if the same thing happens. If so then I know it is the fuel system as well as the muffler I made for it. Will do a pressure test on the bad engine and see if I have any air leaks. I will just bet the front seal is bad. We shall see, will keep update.
The bearing seal isn't what seals the crankcase, it's the oil film created between the crankshaft and bearing race. If you have a leak at the bearing beyond what's normal, the engine likely wouldn't idle well at all. I would put the engine on a test stand with a known good fuel system and run the homemade muffler as well as the stock factory muffler and see if the engine behaves the same. No pressure test is really necessary.