welllllllllllllll...lol, first..yes..chit happens !. but if a person takes their time, uses the correct parts ( or just makes sure parts will work ? ), then you worry about if your work was done right ?. I've been down the same road as the OP many times !, it sucks to rebuild something, and it not run right ?, or something else pops up, that you had no clue there was a problem, or what caused it ?, until you discover it !..lol. had this problem on an old trx350 rancher many moons ago, damn thing ate my lunch and some !..lol. little did I know, that the valve seat could work it's way out of the head once warm/hot ?. I replaced almost everything new with oem, and it still made a rattle when warm/hot ?..that's when I looked into this matter deeper, and found out Honda had a defective head on some of their trx350 rancher heads !..lol.
Interesting and good to know.
The Rancher I've been rebuilding for my neighbor runs good now. It quit burping oil into the airbox (rings must have seated), carb quit leaking with a new float needle, and the disc brakes from a 420 Rancher stop it great.
It rattles like hell though, and I adjusted the valves before I ever tried to crank it.
He got a parts bike with this one, so maybe I'll swap the heads and see if it helps.
if the cam chain is good ?, and valves are set right ?, i'll bank on the valve seat coming out when it's warmed up !..lol. I know this for a fact !. I replaced cam, cam chain, valves were good as far as valve clearance , and it started up great, but once it got warmed up ?, i'd hear what sounded like a bad cam ?, bad cam chain ?, replaced all of that with new oem, still did the same thing. well, after it did it again, I shut it down, pulled the head, and after closely looking at the valve seat under the springs ?, I could see them sticking up ?..asked my bud at my dealership, he says '' oh yeah..those ranchers had a defective head on some of them '' ..now I learned something..lol.
