boovuc 1,090 #1 Posted March 25, 2015 Rod Stewart sang about "Every Picture Tells a Story Don't It"? (Or Doughnut). I now have a parts motor. Compression after decarbon, adjusting valves, replacing a warped head and new gaskets. That repaired oversized valve seat can't be sealing and I'm not throwing anymore money into this engine. Time to find a new spare 16, 18 or 20. Share this post Link to post Share on other sites
niftynoah 25 #3 Posted March 25, 2015 man i love those engines but when they go the become a money pit.putting any more money in it is like Share this post Link to post Share on other sites
Dhodge 528 #4 Posted March 25, 2015 That has good compression compared to the one I just checked. Why cant it just be a head gasket or intake manifold leak on these costly to repair Onans? Share this post Link to post Share on other sites
Red-Bovine 334 #5 Posted March 25, 2015 The Onans are great when running properly. I gave up on mine in my 520H after the third valve seat let loose. That's when I repowered with the Honda GX630. It does a nice job and I'm very happy with the conversion. Red 1 Share this post Link to post Share on other sites
boovuc 1,090 #6 Posted March 25, 2015 I'm debating about just what may be sitting on my bench as a spare for the Onan(s). It may not be an Onan! Share this post Link to post Share on other sites
JackC 617 #7 Posted March 25, 2015 After all the work you have done on the engine, I would at least do a visual inspection of the valve and the valve seat to try to see why the valve is not sealing with the seat. The service manual does not recommend lapping and points out the importance of the correct angles for the seat and the valve. I believe one must be 44 degrees and the other must be 45 degrees or something like that. The interesting point is they do not recommend lapping. If the valve can be made to seat and seal properly you may be good to go. If the valve is off a new valve or reground valve may do it. If the seat is off I would assume it would need to be trued up at a machine shop. You at least have a bunch of good spare parts. Share this post Link to post Share on other sites
Cable 179 #8 Posted March 25, 2015 I've hear that the P220 is still available in Canada from Linemar. Is there any truth to that. I bought a junked 520H a couple of years ago with a Linemar P220 and it is exactly the same, now running on my worker 520H. Share this post Link to post Share on other sites
Sparky-(Admin) 22,242 #9 Posted March 25, 2015 I've hear that the P220 is still available in Canada from Linemar. Is there any truth to that. I bought a junked 520H a couple of years ago with a Linemar P220 and it is exactly the same, now running on my worker 520H. What is Linemar? Is it a clone of an Onan? Or a distributor of genuine Onans? Mike....... Share this post Link to post Share on other sites
ericj 1,578 #10 Posted March 25, 2015 What is Linemar? Is it a clone of an Onan? Or a distributor of genuine Onans? Mike....... the new owner of onan as of several years ago eric j Share this post Link to post Share on other sites
boomers_influence 106 #11 Posted March 25, 2015 club cummins owns onan. in the late 90,s they sold or leased the tooling to linamar to build the the onan engines. the last ones were built in 2005. boo whoever installed the valve seat, did they grind the seat and valve? thank you. boomer ( the used onan engine parts guy ) Share this post Link to post Share on other sites
ericj 1,578 #12 Posted March 25, 2015 the new owner of onan as of several years ago eric j i'll rephrase my statement then as the maker's of onan motors since the mid to late 90's eric j Share this post Link to post Share on other sites
Theroundhousernr 590 #13 Posted March 25, 2015 A test that I have read, was to make sure valve was fully closed and dump rubbing alcohol in the valve chamber. Between the valve seat and rubber valve seals the alcohol was suppose to hold its level for a few minutes without leaking. If it did leak, it was easy to see where it was going. Just a thought. If you have a leak down tester , this would be the quicker, easier option..... Great tool to have. Share this post Link to post Share on other sites
boovuc 1,090 #14 Posted March 26, 2015 Hi Guys, In the post "Opened The Onan Up", WH Nut I think hit it when he said that seat is shot. There are just strange things with that seat and I really believe that what ever shop the original Owner's dealer sent it too messed up that bore for the over-sized seat. My God there were jagged rough edges of aluminum behind the valve that should have never been left there. I will write word for word what was on a work-order from the dealership that the original owner gave the guy I bought it off of. (Hey.........he gave me a pile of paperwork the day I listened to it, ran it and bought it. I had no idea it had extensive work done to it until a few days after I had brought it home). Nice of him to have given me all this stuff about the tractor. From the work order: "Lacking power. Running on one cylinder. Performed compression test on #2 cyl low at 30PSI. Performed leak-down test. Leaking out the intake. Removed engine from frame, removed shrouding, intake pipe, exhaust, valve cover & cyl head. Found valve seat beaten down into the block and cracked block around the seat. Took the block to machine shop for evaluation, machine shop installed a .060 oversized intake seat and counter-bored a little smaller to get a better press fit. Lapped all (4) valves and seats, set valve tappet clearance, cleaned heads, reassembled motor w/ new necessary gaskets, drained oil, replaced oil, replaced oil filter, added fresh oil, replaced spark plugs, serviced air filter, run & test. Adjusted tire pressures and lubricated front end. NOTE: Per machine shop, This is the last time this intake seat can be repaired. No Warranty on this repair". And there you have it! The first time the seat simply dislodged from the block. That was on 10/11/2005. The second seat failure, (above), was from an invoice dated 2/1/2007. In May of 2007, the original owner returned it to the dealership stating it wouldn't idle, only starts on full throttle, surges at mid-throttle but levels out at full throttle. The dealership states they ran it and it seemed fine. No service required. I believe that shortly thereafter, the gentleman I bought it from purchased it and fixed it up as it was in very nice cosmetic condition when I got it. The second owner had it awhile but according to the invoices, he didn't put many hours on it at all. I didn't put much more than 100 hours on it before I too lost compression and THAT is where we are now. I bought it in June of 2011. So that would be me using it about 32 hours a year before it failed in the fall last year. As I wrote in a previous post, after I bought the tractor with the sole purpose of getting a loader on it, I read the service this thing had done to it then went out and bought a spare Onan from Joe's Outdoor Power and that spare motor is now powering the 520. Looking at the angle on that repair and the strange peen marks that are on the seat and off it as well and peen marks that look as though they were obliterated by the re-bore I just don't think I should put any $$$ into anything that includes this block. I don't think the original owner cared/maintained this tractor much. I welcome the comments though. I would do a liquid test of the intake put there is no need. I have a leakdown tester and it is definitely leaking through the intake. The valve is tight on the seat at TDC but that doesn't mean much. I could spin it at TDC before adjusting the valves but I still have the same compression as I had before. Hell the front cylinder is also the same before the decarbon and valve adjustment. (Only 90 PSI). And Boomer, as the work order stated, all 4 valves were lapped after the repair. There are no other service records that give a compression. Hell, it may have had a nominal compression after the repair. Share this post Link to post Share on other sites
WH nut 553 #15 Posted March 26, 2015 It sucks, but sometime you have to throw in the towel. Share this post Link to post Share on other sites
JackC 617 #16 Posted March 26, 2015 (edited) Service invoice said: "Lapped all (4) valves and seats, " ONAN service manual says: IMPORTANT: Do not lap valves. The sharp seating surface between the valve and seat will be removed resulting in shorter valve life. 16. If valve faces are worn, burned or pitted, grind valves to a 44 degree face angle (A) following manufacturers instructions. If valve face margin is less than 0.787 mm (0.031 in. after grinding, replace valve. Another thing that may have been overlooked when the engine was serviced is the following: IMPORTANT: Never reuse intake valve seal. The seal must be replaced each time the valve is removed. Not all engines are serviced the same. Edited March 26, 2015 by JackC Share this post Link to post Share on other sites
gabe911 23 #17 Posted March 29, 2015 Just curious, how many hours was on your onan? Share this post Link to post Share on other sites
