Onan P220G scoring on CYL2 wall

[skippymud]

Hello all,

I don't have the further specs on this engine as the information was not visible when I got it. Best I can guess is that it's an early model P220 (with electronic ignition) based on what OnanParts.com mentions repeatedly when I had bought parts. Their site is very helpful in this regard

So I did a complete restoration on this engine. Upon start-up I noticed a tapping at the CYL2 head. And CYL2 ran about 50F hotter than CYL1. Checked the valve clearance 2X (on both cylinders) and it was good - INTAKE: 0.005 and EXHAUST: 0.013. Reassembled intake and muffler still the tapping. Removed the head on CYL2 and noticed a nice score mark on the CYL wall from top to bottom facing exactly toward the sump, and no visible marks on the piston itself. I am thinking the ring gap is way off on top ring (which I replaced during rebuild). During the interim of my further inspection, does anyone have any thoughts on the cause of the tapping, the scoring and/or the temperature difference?

 

[ILENGINE]

Looks like the cylinder wall in the first picture either has something stuck to it or delaminating. Whatever it is could of broken loose and got stuck in between the piston rings and caused the scoring. Have you taken on of the rings off and slid it into the cylinder to see what the ring gap is. If the gap is too wide the tapping could be a result of piston slap.

But either way that cylinder wall looks like garbage.

 

[Rivets]

Maybe this manual will help. https://www.scribd.com/doc/47347672/Onan-P216-P218-P220-P224-Service-Manual

 

[skippymud]

Hi IEngine

Ring Gap on on this Onan should be 0.003-0.008in. The source of my info is here: www.wersis.net/onan/p220g.html

The actual ring gap is 0.015 which is way out of spec. I will purchase a new full set of rings at OnanParts.com and do a ball honing to see if I can level that out enough to make it function as close to as it should

Thanks much for your help

Ken

Looks like the cylinder wall in the first picture either has something stuck to it or delaminating. Whatever it is could of broken loose and got stuck in between the piston rings and caused the scoring. Have you taken on of the rings off and slid it into the cylinder to see what the ring gap is. If the gap is too wide the tapping could be a result of piston slap.

But either way that cylinder wall looks like garbage.

 

[ILENGINE]

If the cylinder is egg shaped a ball hone will not remove the out of roundness. I would recommend more of a normal cylinder style hone. But without out knowing how out of round or how much taper the cylinder has honing maybe a waste of time.

 

[skippymud]

If the cylinder is egg shaped a ball hone will not remove the out of roundness. I would recommend more of a normal cylinder style hone. But without out knowing how out of round or how much taper the cylinder has honing maybe a waste of time.

Hi back

I took dial bore gauge readings during the rebuilding. Both sides are true and perfectly round left to right and lower to upper - Amazing

So thanks again for the help here. I do have a STD honing tool - A spring-loaded three-stone. Will use that instead of my 3.25" ball hone

Ken

 

[RevB]

Hi IEngine

Ring Gap on on this Onan should be 0.003-0.008in. The source of my info is here: www.wersis.net/onan/p220g.html

The actual ring gap is 0.015 which is way out of spec. I will purchase a new full set of rings at OnanParts.com and do a ball honing to see if I can level that out enough to make it function as close to as it should

Thanks much for your help

Ken

These iron or aluminum cylinders?