Kohler Command CV23 engine teardown questions

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I have a Kohler Command CV23 vertical shaft V-twin installed in a New Holland LS45 (aka Toro Wheelhorse 268-H) mower. History is that the engine has always burned copious amounts of oil since I bought it used a couple years ago, somewhere in the neighborhood of a 1/2 quart per 2 acres that I mow (4 hours?). It runs fantastic, absolutely no trouble or lack of power, but I have to clean the plugs periodically because of oil fouling. It also turns the oil BLACK very quickly, within a few running hours it's jet black after an oil change. I'm tired of breathing oil fumes, so I decided to tear it down and see what the problem might be.

Before this I did a compression test about a year ago, and I got around 200-210 PSI on both cylinders, which is substantially above spec. I double checked it with another compression tester, same result. I chalked it up to carbon fouling/oil deposits in the combustion chamber.

Today I did a leakdown test, but the results were somewhat inconclusive because my new HF Maddox leakdown tester gave me different results each time-- even with the cylinders pressurized at 100 PSI with piston at TDC, I had difficulty hearing any air escaping. One seemed to be 18% leakage, the other 80%, but the next time I checked it the result was different. Evidently Harbor Freight giving their tools a new upscale name and charging 100% more, hasn't improved quality.

I went ahead and tore down the engine to remove both cylinder heads. One head looked like it had an issue-- the exhaust valve stem was covered in wet oil and there was evidence of raw oil exiting the exhaust port. Both pistons/combustion chambers were carboned up pretty good, but this one was particularly bad, the exhaust valve face was covered in wet black deposits, not the normal baked white/brown deposits you'd normally see on the face of an exhaust valve. The other cylinder head looked somewhat like you'd expect, crusty white/brown deposits on the exhaust valve face and stem.

The cylinder walls looked in good shape-- I noticed some very light scoring in the center of the bore on each side (going parallel with piston travel) of both cylinders, but nothing that would catch a fingernail, and nothing I haven't seen in other good running engines. No ridges or anything of the sort at the top of the bore. I was able to rock the pistons back and forth in the bore a bit, perhaps 1/2 millimeter, not sure if that's normal.

Should I just get the cylinder heads rebuilt, or go the whole mile and do cylinders/rings and everything? Part of me just wants to buy a $800 replacement engine and swap it in, but I'd like to keep this repair as cost effective as possible. What do you folks recommend based on the observations I've posted above?
 

92saturnsl2

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swap it.

If not, replace cams too.
Are cams known for going bad on these engines? I'm pretty sure this engine is a replacement on this mower (before I bought it), as this model mower came with a CV18 originally. But admittedly, I have absolutely no idea how many hours are on it.
 
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Are you sure it was raw oil exiting the exhaust port and not a bad valve guide letting oil into the exhaust port.

If it was me I would rebuild the heads with new valve seals and valve guides, re-seat the valves and see if that helps with consumption.

Personally I’d rebuild this one before replacing. If you’re experienced a rebuild kit is likely cheaper than a new motor.

Just my $0.02
 

92saturnsl2

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Are you sure it was raw oil exiting the exhaust port and not a bad valve guide letting oil into the exhaust port.

If it was me I would rebuild the heads with new valve seals and valve guides, re-seat the valves and see if that helps with consumption.

Personally I’d rebuild this one before replacing. If you’re experienced a rebuild kit is likely cheaper than a new motor.

Just my $0.02
The cause of oil in the exhaust port, I'm not sure. But there's definitely raw oil coating the valve stem (which is completely wet with oil compared to the other side which has normal white/brown deposits), and oil in the exhaust port and about 1" into the exhaust downpipe/manifold on that one cylinder.
 
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The cause of oil in the exhaust port, I'm not sure. But there's definitely raw oil coating the valve stem (which is completely wet with oil compared to the other side which has normal white/brown deposits), and oil in the exhaust port and about 1" into the exhaust downpipe/manifold on that one cylinder.
I’m betting it’s a bad valve guide. I can’t imagine raw oil blowing up past the exhaust valve during combustion and leaving oil residue on the valve stem and manifold but not raw oil on the face of the piston or valve head. That would also need to be one heck of a bad ring or scored bore.

Again my money is on a bad valve guide or seal.

Just my $0.02
 

92saturnsl2

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I’m betting it’s a bad valve guide. I can’t imagine raw oil blowing up past the exhaust valve during combustion and leaving oil residue on the valve stem and manifold but not raw oil on the face of the piston or valve head. That would also need to be one heck of a bad ring or scored bore.

Again my money is on a bad valve guide or seal.

Just my $0.02
I'll shoot some pictures in the morning, because there is some evidence of oil in the combustion chamber and valve face too... This is the cylinder the fouls spark plugs rather quickly also (I have to clean the plugs a couple times per season on this cylinder).

I'm less concerned with the other cylinder whose spark plug looks halfway normal, and the combustion chamber has dry carbon deposits, not oily wet ones.
 
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I don't know anything about that engine. But THAT problem is a bad valve guide/seal. I'd be tempted to just replace it and put it back together. Cheap and quick. Replacing a cam would involve splitting the case wouldn't it? Beware of mission creep. :cool:
 
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I’d replace it with a more reliable engine. Kohler Commands are not known for longevity. I’m dealing with a lady who has a 37HP Kohler Command Pro on her new tractor. The engine only has 42 hours on it and it’s already backfiring, failing to start, and a spewing oil out of its exhaust. These engines are beaters.
 

92saturnsl2

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I’d replace it with a more reliable engine. Kohler Commands are not known for longevity. I’m dealing with a lady who has a 37HP Kohler Command Pro on her new tractor. The engine only has 42 hours on it and it’s already backfiring, failing to start, and a spewing oil out of its exhaust. These engines are beaters.
That’s probably the direction I’m headed. I never got to finish the project before weather turned cold (making it no fun to work on), so I’m going to revisit it in the spring.
 
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I’m not familiar with the size of this twin, but for the money I’d be willing to bet on a HF Predator. I’ve enjoyed the one I own but admittedly it had teething pains with the decompression lever sticking in the “let’s break the starter rope and wheel” position. In my case, after disassembly, smoothing metal and still having a few more hard starts, the swift and precise application of a hammer worked every time until it no longer needed it. Runs great, thrifty on fuel, now starts every time, rather quiet.
 
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Just a quick note: The inconsistent readings on your leakdown tester indicate ring problems. Oil will seal bad rings sometimes, and other times, not. Same goes for a cracked ring. Sometimes both piston ring halves will settle into place and seal well enough for a good reading, sometimes they won't.

Anytime I see an aircraft engine with inconsistent leak down tests, and don't hear hissing from the intake or exhaust, the problem is always rings. Most of the time they simply get "soft" (annealed) from overheating.
 
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these engines have a short life. replace it with a kawasaki and thank me later. i run a lawn service and had this same engine, nothing but problems. kawasaki is the way to go. never again a Kohler for me
 

92saturnsl2

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these engines have a short life. replace it with a kawasaki and thank me later. i run a lawn service and had this same engine, nothing but problems. kawasaki is the way to go. never again a Kohler for me
I’ve always had good luck with Kohler command engines. We’d routinely get 5000+ Hours with no trouble in our Lincoln welders. Maybe they didn’t last quite as long as the Onan Flathead engines Lincoln used to use, but the Kohlers are much quieter and smoother running, with more power
 
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If money is the concern, I would put new ring and valve stem seals in it and run it.

Or do nothing and run your used oil change oil in it, you say it runs well, just consumes oil.
 
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