Onan p220G rebuild

[Anthony Wendover 124]

I wasn't sure if i should put this with the 520 tractor rebuild thread im going to start but i figured best to separate the engine form the tractor. So this engine comes off a 1993 520H. It has 473 hours on it. It had a little oil leak in a couple spots so i wanted to take it off the tractor to clean it up. I also had to replace the stator as well as the rest of the electrical components on it. So as i dug into it i said why not just give it a refresh/rebuild. So over the last week i have stripped the engine to the block and the crank. ( did not have much luck pulling the crank gear ) so because everything there looked fine i left the crank in. Cleaned everything up, honed the cylinder walls and ordered my new parts. Thanks to ebay and onanparts.com the rebuild parts should be here by the end of the week. Doing new rods, pistons with rings, cam shaft bearing, valve springs, and all electrical components. One thing that i did notice on my engine was inside of the block. There are a couple chips out of the block around the piston bore. It looks like crappy casting or when the slid the sleeve into the bore? Has anyone else ever seen that inside of their onans?

[Anthony Wendover 124]

Here are the pictures of the cracked missing piece i was talking about.

[WHX?? 46,690]

Looks nice Anthony ...keep up the good work!  Yes those cam gears can be stubborn. Somewhere here ther are some tricks to getting them off. 

Those must be just factory marks. 

[ebinmaine 62,953]

[PeacemakerJack 10,670]

[lynnmor 6,762]

473 hours?  If it had a thousand more than that there might be enough wear to justify rebuilding.  JMHO

[520HC 207]

Yeah I agree completely

[Anthony Wendover 124]

I totally get what you guys are saying about the hours and the rebuild. This is something that did cross my mind and doing the rebuild was not what I set out to originally do. Knowing the person who had this before me who does not maintain or service equipment did play into the fact I wanted to open it up. Also the oil leaks with the need to replace all electronics. I figured if it’s open why not replace some stuff now and freshen it up. If it’s done now I won’t have to worry about it for another 30 years. 

[onanparts.com 178]

2 hours ago, Anthony Wendover said:

I totally get what you guys are saying about the hours and the rebuild. This is something that did cross my mind and doing the rebuild was not what I set out to originally do. Knowing the person who had this before me who does not maintain or service equipment did play into the fact I wanted to open it up. Also the oil leaks with the need to replace all electronics. I figured if it’s open why not replace some stuff now and freshen it up. If it’s done now I won’t have to worry about it for another 30 years. 

 

The bold text in Anthony's quote above says it all folks. Most people don't know how the tractor was maintained by the prior owner or owners. He does know, all the more reason to open the engine up for a thorough inspection. Anthony is "resetting" the clock on his Onan. Most will just roll the dice on a used machine and with an Onan come out OK or better! In this case, he's going for a sure bet.

 

Time and money well spent and invested! The best and most economical time to open up your Onan, is BEFORE it's really tired. That's typically thousands of hours though. At 500 hours and change, it's way too early for Onan engines with proper maintenance history to do a total tear down. But this is not a properly maintained tractor as Anthony has stated.

 

Anthony, thanks for the orders!!! I was able to stop the last one from going out today, just a few minutes before the pick up, and added the 509-0269 seal to it. It will be on the way tomorrow, Thursday.

 

 

[horseyheaven 112]

I agree with Anthony and Onan parts.  I rebuilt my 520h with 1275 hours.  It did not use oil (remarkably) but a valve seat let go.  So, I stumbled on a good block and rebuilt it with parts from Onanparts.com.  Glad I did, it runs strong.  The previous owner did not take the best care of the machine, so I was just trying to turn back the clock.  Anthony, you may want to slot the belt guard to allow for better cooling of rear cylinder.  I also put a remote oil filter on mine to allow more air to flow over the rear cylinder as well.  I found the remote filter and cooler on eBay.  I never have been able to find a good place to put cooler, so it is in a box on the shelf.  It looks like you are doing a great job.  Keep up the good work.  Also, thanks to Onanparts for all the great parts and service.

[chex313 123]

Good thread. 

I just got around to checking the compression on my 520H Onan and it was bad news... 90 to 95 on the front cylinder and 60 to 65 on the back...

 

I'll be following along here, I know I can tear things apart, not so sure about putting it together. lol

Edited May 7, 2020 by chex313

[lynnmor 6,762]

1 hour ago, chex313 said:

Good thread. 

I just got around to checking the compression on my 520H Onan and it was bad news... 90 to 95 on the front cylinder and 60 to 65 on the back...

 

I'll be following along here, I know I can tear things apart, not so sure about putting it together. lol

Before you tear it down, check the valve lash, if they have clearance continue the tear down.  If they are tight, then adjust and recheck compression.  Report your findings.

[chex313 123]

8 minutes ago, lynnmor said:

Before you tear it down, check the valve lash, if they have clearance continue the tear down.  If they are tight, then adjust and recheck compression.  Report your findings.

I am checking how to do that now...I was going to ask you if you have any Onan's for sale, your an 1:45 minutes from me...or get advice on what I needed to do to take it to that NAPA dealer near you.

[lynnmor 6,762]

I doubt NAPA will do more than the machine shop work, here is their website.  If you have time, they aren't hard to work on, just don't push ahead if you are not sure what to do. 

I keep a spare Onan, but not for sale.  The valve adjustment suggestion was to help diagnose the problem and it needs done anyway.

Download the Onan manual

[Anthony Wendover 124]

Guys is my cam worn down? It looks funny but not sure if this is normal or not?

 

its shocking it’s so worn down in that short of hours. What are suggestions to fix it? Replace it or weld and then turn it down on a lath? It also doesn’t fit through the new cam bearing anymore it’s super super tight and gets stuck. 

Edited May 16, 2020 by Anthony Wendover

[lynnmor 6,762]

How does it compare with this one on eBay?  Cam

[Anthony Wendover 124]

The one on ebay looks a lot more worn and more even. mine is worn down egg shaped 

[lynnmor 6,762]

Older Onan engines had points, maybe you are looking at the cam area that operated the points push rod if it were used in an older engine.

[Anthony Wendover 124]

i dont think it is that because the cambearing on PTO side was also worn down on the inside edge. I just dont know if i can reuse this as is or replace it.. Hopefully someone out there knows.. a new one from toro is over 500 

[tom2p 2,393]

32 minutes ago, Anthony Wendover said:

i dont think it is that because the cambearing on PTO side was also worn down on the inside edge. I just dont know if i can reuse this as is or replace it.. Hopefully someone out there knows.. a new one from toro is over 500 

ouch 

 

that's approaching the cost of a camshaft in a $50K 900hp sprint car engine 

 

[onanparts.com 178]

14 hours ago, lynnmor said:

Older Onan engines had points, maybe you are looking at the cam area that operated the points push rod if it were used in an older engine.

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

 

Cam is fine. Lynnmor nailed it. Same one is used for both points and electronic ignitions. If a cam bearing is damaged during install or when removing the cam, the cam will not be happy about going in or out of the block. Very tight cam bearing clearance. 0.0015-0.0030 it does not take much to upset that clearance.

 

Buggered up or distorted it's a no go situation. Bearings should be pressed or pulled in gently, never driven in. Heat block, chill bearings, press in. Very little resistance in the process.

[Anthony Wendover 124]

Thank you for that reassuring and excellent news!! I’ll put it back together sometime this week. Glad to know that the end of the fam is suppose to be a bit egg shaped. Out of curiosity do you have the onan part number for a new cam? I know toro wants a crap ton but I find everything is so much cheaper using a onan part number. If I can find one I’d put it on my shelf as a just Incase. Thank you!!

[onanparts.com 178]

15 hours ago, Anthony Wendover said:

Thank you for that reassuring and excellent news!! I’ll put it back together sometime this week. Glad to know that the end of the fam is suppose to be a bit egg shaped. Out of curiosity do you have the onan part number for a new cam? I know toro wants a crap ton but I find everything is so much cheaper using a onan part number. If I can find one I’d put it on my shelf as a just Incase. Thank you!!

New cams discontinued, P216, P218 & P220. No need to have one on the shelf. When you get North of say 10,000 hours maybe. Onan cams have no history of flat lobes or abnormal wear. If the need ever did arise to replace one there are thousands of used cams in near perfect condition out there. You do not have a disposable cheap Chinese toy motor. Briggs, Kohler V-Twins etc. Odds are very high if you had just serviced it properly it would have outlasted you as is. But since you are resetting the clock to zero, peace of mind does of course have a high value! When the clock gets to around 2500-3000 hours, then it will be time to open it back up for another total look see/inspection/refresh.

[Anthony Wendover 124]

So update guys. This thing is starting to go back together the last couple days. Pistons are in along with the camshaft. Had to lightly sand down the ends of the camshaft with very fine grit emery cloth to get it to slide into the new bearings. So far this thing is super tight! Getting the valves in today and then start going over everything. Should be ready to fire in a couple of days time!

[Goofey 89]

On 5/18/2020 at 9:08 PM, onanparts.com said:

You do not have a disposable cheap Chinese toy motor. Briggs, Kohler V-Twins etc.

 

You are not just a little bit biased are you