Generac 15KW generator engine tear down

[KYErik]

Was it blowing lots of blue smoke out of the exhaust under load while it was burning all of that oil? (blue smoke under load would indicate an oil control ring issue)

When you did change the oil did it look like it was full of shiny metal "dust"? Another culprit could be stuck oil control rings (the rings may be in spec but they are just all gummed up in the piston grooves and can't "float" and stay tight against the cylinders).

 

[kennyd]

I hope I never have to see the inside of mine!

 

[tcartwri]

I noticed that only the intake valves have seals:

I don't think the guides are replaceable, at least I don't see a part number for them in the Generac manual.

Here's a close up of the #1 valves after I removed them. It looks like oil deposits on the intake valve.

So would my best bet be to take the heads and associated parts to a small engine repair shop and have then redo them?

Seals on the intake only is fine. When they do the guides, the original is oversized slightly and then a new sleeve is pressed in and honed to size. The guides do 90% of the oil control. You would be far ahead of the game to go to a proper machine shop.

I still do not have an answer as to what is forming those deposits on the exhaust valve. I've never seen anything like that.

 

[tcartwri]

Ok, from a little bit of research it sounds like it was the oil you were using. 'Apparently' an LPG engine requires low ash content oils. The deposits on the valves are carbonic ash, that is distilled out of the crankase oil by the heat of the chamber. Never heard of this, but apparently it is a known issue with lpg fuel.

ConocoPhillips Lubricants Expands Natural Gas Engine Oil Offering

 

[pclausen]

I'd take the heads to a small engine guy and have him do a valve job on them.. Then put them back on.. Set the intake and exhaust to .076mm Set at TDC cold..

Appreciate the advice, that's what I'll do and make sure he does the guides as well.

 

[pclausen]

Was it blowing lots of blue smoke out of the exhaust under load while it was burning all of that oil? (blue smoke under load would indicate an oil control ring issue)

The exhaust had no color to it at all.

When you did change the oil did it look like it was full of shiny metal "dust"? Another culprit could be stuck oil control rings (the rings may be in spec but they are just all gummed up in the piston grooves and can't "float" and stay tight against the cylinders).

The oil did not look unusual at all. I poured an ounce or so of fresh engine oil into each cylinder about 6 hours ago. Its all still there.

 

[pclausen]

Ok, from a little bit of research it sounds like it was the oil you were using. 'Apparently' an LPG engine requires low ash content oils. The deposits on the valves are carbonic ash, that is distilled out of the crankase oil by the heat of the chamber. Never heard of this, but apparently it is a known issue with lpg fuel.

Thanks Tim! I read the link you sent me and it sure sounds like that is why it happened, especially being that temps were around 100 degrees and the generator was running at close to 100% load for days.

 

[murphy1244]

Pete, was this the unit with oil sending unit leak?

 

[pclausen]

Seals on the intake only is fine. When they do the guides, the original is oversized slightly and then a new sleeve is pressed in and honed to size. The guides do 90% of the oil control. You would be far ahead of the game to go to a proper machine shop.

Appreciate the advice. I'll ask around to see what is a good shop around here.

 

[pclausen]

Pete, was this the unit with oil sending unit leak?

No, that's my current 8KW unit. I got the new oil sending unit, but haven't installed it yet. The 8kw is a vertical shaft V twin with a belt drive. I'll probably swap it for the 15KW unit, and then tear it down to see what condition it is in. It will likely have similar deposits on the exhaust valves.