Took head off 20 hp kohler.

Finally got around to it, removed the head on left side #2. The small engine repair shop said I have a blown head gasket. He also recommended I replace valves while I had it apart. He wanted $100 to replace valves. I spent $10 on a gasket set for one head.

Well no blown head gasket where he said I would have one, but he was right about valves. I've read where valves seems be be a problem with kohler commands.

I used tools today that haven't seen day light in 40 years. Instead of buying new valves, I just lapped the old ones in. Then I did a leak test using K1.

I let it run at about 2400 for about 20 minutes then measured exhaust temps, both reading the same 575. That never happened in the past. The bad, dirty burning cylinder was always a good 100+ degrees cooler.

Time will tell if I solved the problem. You can see from the muffler which cylinder was burning clean and which wasn't. Keep in mind, there is only one carb for both cylinder.

This kohler has 1600 hrs and I was surprised to see very little scaring and no ridge on cylinder. If this doesn't fix the problem, I'll just run the engine until it blows.

After pulling the tractor back inside, I noticed it left oil on the concrete. Something in they hydrostatic pump area. Job for tomorrow.

Good clean up job. Looks like a good job.
I hate getting into something like that though. I love tinkering so much that the first thing I would have noticed is that it has way to much firing chamber. I would not have been able to put it back on without taking it to a mill and reducing it. ^D

I'd rather of ground the valves and narrowed up the seats a bit. Did the seats meet specs. ?
Were there any clean spots on the piston tops before cleaning them ? If so that would indicate oil coming up past the rings in that area.

Do they use valve stem seals?

Did you replace them?

Is the fit of the valves in the guides "within spec.)?

Looks like the cylinder is scored a bit, which likely explains the carbon deposits.

I would guess from what I can see of the valve seat and the cleaned up valves that it didn't need a valve grind. A little lapping would be fine or not. I would not want the seat any narrower than what I see on anything. It would beat a groove in the valve.

Like This!

sort of looks like the old VW Beetle 'firing chamber' after 'hemi cut' valve job to reduce squish area, promote even burn across chamber and slight reduction in turbulence leading to even high temperature in aircooled engines. Arguments both ways- Chevy small block wedge with squish/quence area to one side or Harley and BMW hemi chamber. Aircooled head/combustion chamber has 100 degree hotter 'residual' heat to vaporize fuel droplets compared to water cooled head hat may need a bit of 'swirling' of intake charge during compression for even distribution of fuel for even ignition or a 'push' of fuel toward spark plug. Piston top is the other factor- is it flat topped or a slight side 'bulge' across from spark plug to give the squish effect, higher compression while leaving some valve clearance? RN