dcairns560 6 #1 Posted August 29, 2022 Ive got a 16hp Onan in my D160 with front end loader. Over the winter I pulled the engine to fix some oil leaks and replace the rings as it seemed to have a abnormal amount of blow by. Cleaned everything up, replaced exhaust valve guides, honed cylinders and installed new rings and buttoned everything up. After fixing some ignition and intake manifold issues, it ran great and I used it heavily for probably 15 hours. While moving some dirt, it suddenly started to rattle a little and then BANG, broke a connecting rod on the right cylinder. It also broke the piston skirt in that side. I bought two new upgraded rods, a used crank and a used piston. Everything else inside the engine looked good. Once reinstalled, it ran fine. Went out and started working it and smoke started billowing out of the exhaust on both sides. I found that there was a large amount of oil being pushed out of the breather hose and into air cleaner housing and being sucked into the carb. It passing so much oil that its dripping out of the air cleaner housing. I did not measure the used piston before installing and reused the same rings that I had installed over the winter. I thought maybe the used piston was severely worn but today I checked compression and both sides are at 110psi. Any thoughts on what I should do next? Share this post Link to post Share on other sites
ineedanother 1,668 #2 Posted August 29, 2022 42 minutes ago, dcairns560 said: Ive got a 16hp Onan in my D160 with front end loader. Over the winter I pulled the engine to fix some oil leaks and replace the rings as it seemed to have a abnormal amount of blow by. Cleaned everything up, replaced exhaust valve guides, honed cylinders and installed new rings and buttoned everything up. After fixing some ignition and intake manifold issues, it ran great and I used it heavily for probably 15 hours. While moving some dirt, it suddenly started to rattle a little and then BANG, broke a connecting rod on the right cylinder. It also broke the piston skirt in that side. I bought two new upgraded rods, a used crank and a used piston. Everything else inside the engine looked good. Once reinstalled, it ran fine. Went out and started working it and smoke started billowing out of the exhaust on both sides. I found that there was a large amount of oil being pushed out of the breather hose and into air cleaner housing and being sucked into the carb. It passing so much oil that its dripping out of the air cleaner housing. I did not measure the used piston before installing and reused the same rings that I had installed over the winter. I thought maybe the used piston was severely worn but today I checked compression and both sides are at 110psi. Any thoughts on what I should do next? My initial thought is not to install another used piston. Possibly not in spec or out of round. The new ring may giving you an acceptable compression check (cold) but likely not when the engine is hot. This isn't my area of expertise though and others will surely chime in with reliable information. Share this post Link to post Share on other sites
kpinnc 14,625 #3 Posted August 29, 2022 I'm inclined to agree with the previous post. A used piston can be OK, but only if it is checked for out of round and the ring slots are good, among other things. Onan specs are much tighter than many other engines. What you get away with on an old briggs probably won't last in an Onan. I didn't see any mention of checking the cylinder bores. The taper and out of round specs are pretty tight, and usually what forces you to get a fresh bore on a reduild. Your mention of the skirt breaking on the piston makes me wonder if the cylinders needed a fresh bore and oversized pistons. But these are just opinions. No one can diagnose your engine on a forum. If you want it done right, stick to the service manual specs. 1 Share this post Link to post Share on other sites
squonk 43,774 #4 Posted August 29, 2022 Once rings are worn in and then removed and installed on another piston, they don't like to seal real well. 2 Share this post Link to post Share on other sites
Snoopy11 5,718 #5 Posted August 29, 2022 2 hours ago, squonk said: Once rings are worn in and then removed and installed on another piston, they don't like to seal real well. THANK-YOU! ALWAYS replace the rings. Just a cheap insurance precaution... Don 1 Share this post Link to post Share on other sites
