My kohler k341 from my cub 1650 has been burning some oil, especially on startup, and I need some experienced opinions. The motor runs fine and seems to have adequate power but it smokes,. I pulled the head to check it out and found that the exhaust valve had what I thought was excessive side to side play when fully opened. I assumed that either the valve guide or valve stem (or both) was worn resulting in this side to side play.
I took both valves out and measured the stems with a digital caliper with a rated accuracy of + 0.001". Both valves were within spec. However, the exhaust valve looked like the stem diameter was smaller about 3/4" below the valve face. This was in a non-mechanical wear area and I was surprised to see it. Anyway, I measured that suspected area and sure enough the measurement was about 0.017" smaller than the rest of the stem.
I had no way of measuring the ID of the valve guides but I knew that the OD of the intake valve was larger than the OD of the exhaust and measured about 0.310 - 0.311". Since the Kohler manual calls for reaming newly installed valve guides with a 0.3125" reamer, I assumed the guides would be at least 0.3125" ID or larger. I tried inserting the intake valve stem into the exhaust valve guide. If it fit, I would know that the ID of the exhaust guide was at least as large as the OD of the intake valve stem and if it still had significant side to side play, the guide would probably need to be replaced. The intake valve stem wouldn't go into the exhaust guide so the ID of the exhaust guide is less than 0.311". It also means that the ID of the exhaust guide is less than the diameter of the reamer that Kohler recommends using for new guides which surprised me.
The cylinder bore looked really good and measured within standard spec for diameter and also for "out of round" and "taper". I didn't see any evidence of damage to the cylinder walls. The crankshaft measured right at the maximum wear limit but with the accuracy of my digital calipers it could be out of spec by up to 0.002" or within spec 0.001" above the maximum wear limit. I think the crank is OK because the connecting rod to crank clearance measured 0.002" with plastigage. This is within the maximum wear limit listed by Kohler. The connecting rod also looked good and the bearing surface showed no evidence of overheating or scoring. The piston also measured within standard spec with only a slight amount of scoring, about 1" wide, noted in an area above the top ring. I measured the piston ring end gap for the old rings and I think I now know why it was burning oil. The top ring end gap was 0.033", the second ring end gap was 0.072", and the oil ring gap was 0.173". Maximum wear piston ring end gap from the Kohler specs is 0.030". In addition, the ring gaps weren't staggered 180 degrees as recommended.
There were no balance gears and I don't know whether or not this engine ever had them.
The engine looks like it's been opened before as there was some RTV silicone gasket sealer on the oil pan gasket. Don't know what if anything was done when the engine was opened.
Based on what I found, I'm thinking I will simply do a light cylinder honing, replace piston rings with standard size (possibly new standard piston too), and new valves. Any thoughts or suggestions would be appreciated.