Haunted Onan, (More Stuff)

[boovuc 1,090]

More on the Onan I took off my loader.

Recap............30 PSI compression on the rear cyl. Won't fire the rear until it warms up.

 

1. Tremendous amount of carbon build up and more so on the front cyl than the rear. 

 

2. Found The .060 oversized valve seat. (The second rear seal fix the engine saw by the first owner). It was peened in but that some of the peen marks are obliterated and others I see are not even on the valve seat!

 

3. Adjusted the valves today. Both cylinders valves were out of adjustment. Both rear valves were WAY out of adjustment. 

 

4. Insult to injury, I think it was HorseFixer that said to put the heads on a plate of glass to see if they are warped and use the glass to mark where to grind them. I got my plate glass out and sure enough, the rear cyl head is warped. Pretty bad I might add.

 

I'm going to get another head for it. (Not screwing around with it). It's no wonder I only had 30 PSI on the rear. The front should be much better than 90 PSI now also. Once I get it back together, I'll do a leakdown after a compression check to see how bad it really is. For now, it will work as a backup but not for long if it was needed to be pressed into mowing duty. The loader isn't used on a daily basis in the summer so I'll be fine with this as a spare and the much newer, lower hour P220 that is on it now hopefully will last a long long time!

[JackC 616]

"Both rear valves were WAY out of adjustment. "  

 

There you go.  We must do the valve checks if we want long life out of our ONANs.  One member said most heads eventually warp and need periodic attention.  We all need that flat piece of plate glass to do the head checks.  

 

One ONAN service manual said to de-carbon more often if the engine is run at lower rpms.  One eBay seller of gaskets recommends to de-carbon and adjust valves every 200 hours.  With the Performer Series engines it seem best to run them hard and check them often.  They are not the bullet proof, run them any way you want for years, cast iron engines that we are used to in the older models.  As far as I am concerned, nothing beats the sound of an ONAN Performer Series engine and I keep spares just in case.