Kohler K301 engine breaks up

[Erich]

Hi, I'm new to the group and I hope one of you can help me with my Cub Cadet 127 with a Kohler K301 engine.

It was running fine this winter and I did some good snow plowing with it. Early in the spring, while starting up, she backfired once and then wouldn't start easily. Wen it did, it wouldn't rev up and kept breaking up and backfiring and had no power under load.

I thought it was an ignition problem and so replaced everything in the ignition sytem, one item at a time, with no help. I replaced the plug, the coil, the points and condenser, bypassed the switch and put in a new wiring harness.

A local dealer told me it might be a valve problem, so I tore off the head and sure enough, she had a fairly pitted exhaust valve, which I was able to reseat. I also checked for a sheared flywheel key, as long as I was tearing into it, and after breaking two shroud bolts, found the key was intact. Unfortunately, when I started it up, it had the same symtoms.

I find I can get it to run a bit better if I open the point gap way wide. It runs a bit smoother, right up until the spark quits entirely, but it never gets to the point where it has real power at high RPMs and it still will backfire occasionally at high RPM with no load. As soon as I put a load on it, it sputters and dies. Also, when shutting it off, it backfires through the muffler after the engine has stopped. I had to replace one muffler already because of this.

I also checked for fuel flow and it seems fine, although doesn't make sense to me that it would be a fuel problem since it does run somewhat better and faster when I change the spark timing.

I'm at my wits end and I've already invested well over $200 and a lot of time trying to find the problem. I hate to have to throw away such a nicely built, cast iron, ball bearing engine to replace it with something that will be expensive and probably less robust than what I have, but I don't know what else to do at this point. Can anyone here offer me a clue?

Thank you,