I recently acquired a 7kw generator with a Honda GX390 engine on it, first Honda small engine I've worked on. Engine runs beautifully and generator works perfectly, for a couple of minutes anyways. Then I start getting oil coming out of the breather tube into the air filter box, which gets sucked into the intake and the engine starts belching white smoke as it burns off the oil which is now running everywhere.
I've changed out the valve cover, hoping it was the breather valve that was bad, and that did not help. Engine does not have too much oil in it, already checked that. Best guess is over pressurization of the crankcase forcing excess oil up into the valve cover. Started the engine briefly without the valve cover on just to see what was going on and the amount of oil coming up through the oiler passage seemed pretty excessive.
My question, for those who know these engines well, should I be looking at replacing the head or tearing the whole engine down and replacing the piston rings? I can't think of anything else that would cause this issue, and what little I've been able to find in forums leans towards one or the other of those being the problem. I do have a compression tester set, just haven't had a chance to check the compression on it, but a leak down would probably be a more suitable test anyways.
Any thoughts or suggestions would be greatly appreciated!
