dr363305 50 #1 Posted October 2, 2022 (edited) Hello and welcome to my second post. As previously stated, I just purchased a 1988 520-H with 1192 hours showing on the hour meter. I had also stated earlier in my introduction post that I noticed some blue smoke on throttle up and down. I have maybe used it for a total time of 2 hours and that has been enough to drop the oil just to the tip of the dipstick. I verified that the previous owner had changed the oil recently due to it being very new looking oil and at the proper fill mark. Also confirmed that the crankcase vent is venting and there is no sign of mass amounts of oil being pushed up by the air filter. Cylinder compression at the time of purchase was both cylinders over 100psi. The engine still runs strong aside from the burning oil. Also, at one point during my ownership, the engine seemed to “clear up” and revs increased from 3300rpm to about 3800rpm under full throttle. It did this once and hasnt done it again since. So, my questions are as follows: 1. What should I check that would help the veterans here diagnose my issue faster? 2. What should I prepare for in terms of a refresh? Hone and new rings? Piston kit? New rod and main bearings? This has the potential to be one of those “while you’re in there” type of situations. Definitely open to all credible suggestions. 3. Are there any other reputable onan parts distributors aside from onanparts.com ? I was looking and it seems like a lot of would be critical replacement parts are out of stock. Feel free to let me know your thoughts on my issue. Thanks in advance! Edited October 2, 2022 by dr363305 More Information Share this post Link to post Share on other sites
cleat 6,034 #2 Posted October 2, 2022 What oil viscosity was used I wonder . I find 30W single grade works best to prevent oil usage. 2 Share this post Link to post Share on other sites
dr363305 50 #3 Posted October 2, 2022 4 minutes ago, cleat said: What oil viscosity was used I wonder. I just changed it to 10w40 full synthetic. Share this post Link to post Share on other sites
lynnmor 7,307 #4 Posted October 2, 2022 The engine over speed is likely caused by the governor flyball spacer coming loose as the engine heats up. The engine may have been damaged by the previous owner if he ran it while the engine was spinning too fast. The spacers are now being made by at least two vendors, do a search. It may be that your oil rings are spent causing the oil consumption. As you know the wear won't be known till you open it up, if oil rings are worn it may be that the air filtration was poor. Your reading of 100 PSI is good however there may be a considerable amount of carbon causing a false reading. I use Kohler SAE 30 oil since it has the correct amount of ZDDP to prevent wear, SN rated oils should be avoided. I had several vendors for Onan parts but I checked right now and they are gone. Contact Boomer, you will find him very helpful and has new and used parts. 1 Share this post Link to post Share on other sites
dr363305 50 #5 Posted October 3, 2022 Appreciate the help! Thank you! Share this post Link to post Share on other sites
lynnmor 7,307 #6 Posted October 3, 2022 2 hours ago, dr363305 said: Appreciate the help! Thank you! Keep us posted on your progress, there may be more questions. Share this post Link to post Share on other sites
dr363305 50 #7 Posted October 4, 2022 I know there will be. It will just take some time. Hopefully I get to it this winter. I have another massive engine undertaking to knock out this winter as well, so lets all hope things go smoothly. I did have one last immediate question. Does the P220G have rod bearings? I have searched and have only found main bearings. This is potentially a stupid question so feel free to roast me for it lol. Share this post Link to post Share on other sites
lynnmor 7,307 #8 Posted October 4, 2022 No rod bearings, you replace the rod, undersized is available if needed. 1 Share this post Link to post Share on other sites
