Jake217 20 #1 Posted March 19, 2013 Hey All, I just finished refurbishing the P220G in my 520 H. She was puffing oil smoke on start up and I was beginning to notice some smoke when running. Compression was really good (125 psi in both), but I tore it down anyway. Everything mic’d in spec, so I just replaced rings, valve guides (what a pain) and intake valve seals. I could still see the original cross hatch in the cylinders so just gave them a quick deglaze. Rebuilt carb, new fuel lines, gaskets, oil, quick valve lap, etc. I did add an electric fuel pump too. The engine runs great, but I’m getting a knock on cold start that seems to go away as the engine warms up. I know I torqued the connecting rod bolts correctly as well as every other bolt. I listened with a mechanics stethoscope and can’t hear anything along the block at the crankshaft at the PTO or down at the pan. I’ve seen a couple of threads that mention in passing that there is a knock in their Onan when cold but no responses. Is this something I should be worried about? I’m thinking it just might be piston slap which I suppose I can live with, but I would like to hear from any experts. I don’t want to rip the engine out again to drop the pan and look at the crank unless I really have to. Crankshaft end play is within spec too. What’s my best course of action? Thanks Jake Share this post Link to post Share on other sites
chrisd200(inactive) 56 #2 Posted March 19, 2013 Had a Onan once that did something similar. Ended up just being a noisy valve that was making the noise and needed adjusting. The sound it made was a very strong, solid click/tap more than a knock though. And yes, the valve guides and seals are a pain. Got an Onan in a D160 that doesn't seem to be oiling. Gonna have to open it up I guess. Good luck!!!!!!!!!!!! Share this post Link to post Share on other sites
JackC 617 #3 Posted March 20, 2013 Never heard any knocks from the 6 ONAN engines that I have. At least it goes away. Maybe valve related since that is where some work was done and changes made. Maybe recheck the valves and valve clearance? Share this post Link to post Share on other sites
JackC 617 #4 Posted March 20, 2013 "quick valve lap". You are not supposed to do that on the P series. Check the service manual. "By grinding the valve face and seat at slightly different angles, a fine line of contact on face and seat is obtained, eliminating the need to lap the seating surfaces." Share this post Link to post Share on other sites
