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?
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?