the engine was a Kohler Courage. My opinion is that these are better used as boat anchors than an actual engine. It was nothing but trouble for me. About anything and everything that could go wrong with it did. I had another one and it at least didn’t linger like this one. It just blew one day. I have a few Kohler Commands (commercial line) that I run as hard as they will run and they just keep coming back for more. I change the oil once per year and that is it. The Courage is the cheaper consumer line and it is junk. Spend the extra bucks for a commercial engine.
I think the comment about an air leak was right on. I always had the feeling this engine was pulling air from somewhere it it would run away even when throttled down. I think the air leak as well as the oil leak was internal. I have always wondered about a blown head gasket between the pushrod gallery and the cylinder. I made sure all mounting bolts on the various flanges were tight and visually inspected everything. I even tried the carb cleaner/starting fluid trick around likely leaks and never found a thing. I wonder if it was coming through the engine seals. These were leaking quite noticeably towards the end of this thing. Oil would pour down from under the flywheel and run down the sides of the engine. Maybe it was sucking air into the crankcase through an engine seal?
The Commands were also known for cracking the block under the flywheel but more so on the single cylinders. This was a twin but anything is possible.
Then one day it had a fire. The thing was running so hot that this didn’t surprise me. All that oil and the crud that stuck to it just flashed over one day and caught fire. I almost abandoned the mower where it sat but figured I would take my chances and drive it the 1/4 mile or so back to the house. I sprayed it with the hose from a distance which I know is the best with an oil fire but I put it out. The thing continued to run and scream in runaway condition for several minutes until I got it cooled down enough with the water that it turned off. All the ignition wiring was burned through so it was definitely running without a spark. I repaired the wiring harness and went on with life.
It was definitely burning oil. How else would you account for the oil consumption and smoke? It wasn’t leaking much oil until near the end. The smoke was horrid until warmed up, then it would flash over to flames. It may not have been burning pure oil and had help from the gas that was mixed in but think the oil was burning. I literally was stopping every 10 minutes to add oil by the end.
The only thing restricting the speed of the engine was the amount of oil it was burning. Basically, could tell that at higher RPMs it was pumping more oil into the cylinder and it would start to bog down and smoke because it simply couldn’t handle that much oil. Here is another video kind showing this self-limiting behavior.
https://www.youtube.com/watch?v=h0JenRQvFkQ Basically it would run this way RIGHT before it flashed over and went to flaming out the exhaust.
The stop solenoid was another issue with this thing. It seemed to work most of the time but when it didn’t, it would always fail closed while I was mowing. Then there were the backfires this thing was meant to prevent. They sounded like an explosion and eventually blew the muffler to pieces while I was mowing and mowed over them. I shut the mower off at a neighbor’s once and they said the mower must have exploded. I told them this would just happen and that it was nothing that odd for that engine.
I had a chainsaw run away to destruction once. A tree had fallen on it several months prior. It was a Stihl so I rebuilt it from parts off a junk saw that I had laying around. It never ran quite right after this and would guess it had an air leak. It would be very temperamental in that you couldn’t keep the fuel/air mix straight. It would lean out and start to run away so I would enrich the mix. Then it would choke down and start smoking as if run too rich, then I would lean the mix. It was always this way after the tree fell on the saw. Anyway, I was cutting a pretty large branch one day and the saw started running away after I unloaded and throttled it down. I just kept on screaming. There was no choking it down. It just kept on screaming in runaway condition. I just held onto it and kept it away from anything I didn’t want harmed as it ran away. Then it finally started to slow down as molten pieces of the engine were emitted from the exhaust. It then locked up tight as a drum! I knew it was trash after the tree fell on it so any extra use was a bonus.