I had a Kohler KT730 (Spec 3035) with about 75 hours on it lose a camshaft, so I was repairing it under Kohler's warranty. The black plastic gear shattered, and little pieces of it were everywhere.
So today I put in the improved style camshaft, 4 new push rods (they were all bent), a new oil seal, a new oil filter and fresh oil, and put it back on the mower (Country Clipper zero turn). When I started the engine, it made a horrible racket for about 5 seconds, but then quieted down and ran well. I noticed that whenever I accelerated the engine, it was noisy during the acceleration, and maybe a little at higher RPM's. But it sounded quieter at lower speeds. I figured out later that the muffler has a loose baffle, so that may have been the noise.
But the main problem (aside from the fuel pump leaking almost directly over the muffler ) was that, after maybe 90 seconds of total run time (I started and stopped the engine 3 or 4 times), I stopped the engine and tried to start it up again. The starter gear hit the flywheel, but it wouldn't turn over! Locked up! So I removed all loads to the engine to make sure it wasn't something on the equipment causing my problem. Problem is definitely in the engine. I put a wrench on the PTO bolt to try to turn it, and it wasn't going anywhere. So I pulled the engine back off, drained the oil (no, I didn't forget to put oil in it!), and took the crankcase cover back off, not having any idea what I'd see inside. Everything looked fine in the crankcase. No scored bearings, no heat discoloration, nothing broke...it all looked like it should. Then I took the rod caps loose, and they looked good. The connecting rod bearings and crank journal looked fine as well, and the pistons moved freely up and down the cylinder. I saw and felt as much of the cylinders as I could from the bottom end, and the pistons still in place, and there was no scoring that I could tell. But the crank still would not turn, so I figured it must've seized at the magneto bearing. So I removed the flywheel and tapped the crankshaft loose, and much to my surprise, the upper bearing looked just as pristine as everything else. So did the crankshaft at that spot. Why on earth did the engine lock up?
Of course, this happened late on a Friday afternoon when I have to wait till Monday to call Kohler for any support. I slid the crankshaft back in place and buttoned the crankcase cover back on with 2 bolts, to see what the end play was. None. I thought all engines needed crankshaft end play, so this may be a problem. I'll have to reference the service manual for that. There is no gasket for the cover, just an RTV sealant. Problem is, it's been running 75 hours without locking up, and I only changed the camshaft, so I have a hard time saying a lack of end play is what caused the engine to lock up this time. I'm really at a loss here. Any ideas?