520H Onan P220 Questions

[chex313 123]

I am determining whether to save this P220. I am at the point where I am adjusting the valve's ( Could not find my 60 year old feeler gauge) I picked one up at Napa. 

I wanted to see the TC mark on the flywheel mentioned in my service manual, but the mesh screens screws were stripped. I assume I need to get that off to see the mark. I can not see it otherwise. 

 

I can turn it on the pulley side but things are backwards than. If I just get the pressure off so I can turn the valve is that enough to adjust that cylinders valves or do I need to follow the exact directions...Was not sure if that was just the easiest guideline to get the valves pressure off or an actual rule. So I stopped to read old threads and look at an Arndt youtube on it.

 

After the .005 intake and .013 adjustments how much do I need to put back together to test the compression again?

 

[chex313 123]

lynnmor, from Anthony's build thread...

 

Quote

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 wanted to get more info before I adjusted them , but from what I can tell the exhaust tappet's seem tighter than .013 on both sides. The intakes are wider than .005. 

That is a good thing correct?  I see a good amount of carbon but I did not see a valve seat out.

Edited May 9, 2020 by chex313

[lynnmor 7,285]

If an intake valve has way too much clearance then there is a good chance that the valve seat has loosened.

 

To adjust the valves on nearly all four cycle engines you don't really need to see the timing marks.  Rotate the engine till a valve is pushed completely open, mark the pulley or flywheel and then rotate the engine one complete turn, it doesn't need to be precise, now adjust that valve.  I use chalk to do the marking.  Do each valve the same way.

 

The reason for doing the valve lash check before teardown and checking compression is to get an idea of the condition of the rings.  If by chance the readings come up to satisfactory, then you might be able to skip a complete teardown and the compression loss may have been simply the valve leakage.  You can check compression with all those parts missing.

 

Its good to see that you plugged the openings, if you remove any valves, plug those small oil return holes as well to prevent the keepers from falling in.

 

Not necessary, but if you want to see the timing marks, simply remove that big rubber tube sticking in the blower housing and look in there.

 

[chex313 123]

Thanks Lynnmor, Every time I read one of your posts I learn 100% more than I knew the day before. 

[chex313 123]

On 5/7/2020 at 4:28 PM, 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...

[chex313 123]

Those were my readings I posted in Anthony's thread...After adjustment the front cylinder is the same around just over 90 the back came up from just over 60 to just under 90...They are within 10 of each other now...I can adjust them again and see if I can improve it any.

 

[lynnmor 7,285]

No need to readjust if you did it right.  The compression is a bit low, but you can run it.  If you are going to reassemble at this point, do check the compression multiple times to see if something is going on.  I had an engine with good compression and found a loose valve seat when I pulled the heads for carbon removal.

[chex313 123]

47 minutes ago, lynnmor said:

No need to readjust if you did it right.  The compression is a bit low, but you can run it.  If you are going to reassemble at this point, do check the compression multiple times to see if something is going on.  I had an engine with good compression and found a loose valve seat when I pulled the heads for carbon removal.

Thanks Lynn, I checked them each 3 times running the starter 8 seconds and the numbers were as identical as they could be. I do not have gaskets yet. So I plan on going over the adj one more time.

 

Things always seem easy , once you have done it once...

 

 

Edited May 11, 2020 by chex313

[chex313 123]

So here is where I am at...Got it running with the valve adj (Thanks Lynnmor)...Its year old gas with no stabilizer and its running pretty good. Its got 1400+ hours....Had 1200 hours on it when I got it about between 18 and 20 years ago($500). It lost a valve seat around 10 years ago. It was my only Tractor and I needed it fixed ASAP. According to the receipt $100(Labor was $$$) for the one valve...I do not think they did much else...Not sure...Local WH/Toro but they sent it out to machine shop.

 

I now have the time to care for it. I also do not need to use except as a spare. 

 

So do I pull it and drop an HF 13HP in it? (Its broken in and ready to go) Fix the 220P to the best of my ability and have the ONAN as a spare after its reconditioned. Or stick it back in and get rid of the HF (Only have $325 in it plus a few parts.) I need to move it and pushing or towing are not good options...Its going to take me a long time to work on the engine, it will be my first small engine ever, and I have not done any kind of major engine work since the 70's. Both engines at half throttle.

 

 

Edited May 19, 2020 by chex313
add

[lynnmor 7,285]

That sounds like another valve seat, only way to know for sure is to tear it down.  You could do Plan C and sell it to me as is.  I keep a spare engine that I could swap into it and then rebuild that one for my spare.  If you could find a good tractor that needs an engine, then stuff the Predator in it.  Many options.

[chex313 123]

2 hours ago, lynnmor said:

That sounds like another valve seat, only way to know for sure is to tear it down.  You could do Plan C and sell it to me as is.  I keep a spare engine that I could swap into it and then rebuild that one for my spare.  If you could find a good tractor that needs an engine, then stuff the Predator in it.  Many options.

Your ears are better than mine Lynn I can't tell anything by the sound...

 

If you mean get rid of the whole tractor , there wouldn't be much fun in that. Its not worth anything to sell. Its only useful as a project. 

 

If I don't do anything with the Onan once I get it out , I'll get it to you.

Edited May 19, 2020 by chex313

[Greentored 3,201]

@chex313  you can yank the intake back off and nearly see the intake seat, which is the one that normally lets go, and normally the rear. Put your finger on it, roll the engine over by hand til the valve opens, and see if you can move the seat.