Issues with Cub 1650/kohler k341
 

Hello,

I need some opinions. Got a 1650 with a 341 in it. The motor had new rings put in because it smoked. When I first got it there was a knock. Maybe was ran 30-45 minutes like this that I know of. I adjusted the valves, points, and plug gap and the knock disappeared. So I put the deck on and mow for 45 minutes. Ran strong and no knock. Slight bit of smoke out the breather that you could only see in just the right sun light. Nothing substantial I didnt think. I mow the whole back yard without issues. Make 2 laps around the house and the breather begins to smoke pretty bad. I look to investigate and its pushing oil out of the governor rod and the breather vent. Engine built 120psi compression cold, 15 psi leak cold, 5 psi leak when warm. Starts and runs fine when cold. After about 5 minutes the breather begins to smoke and then oil collects and also pushed out the governor rod. Took the head off and have a oily film all over the chamber. Also was pushing some oily exhaust out the flywheel side of the gasket and exhaust out the pto side as there was carbon residue on and past the gasket. Also i think the head may not have been torqued completely, the bolts were very easy to loosen. Cylinder measures only 3 thous out of spec at most, head is 4 thous out of flat in one spot. Should I just put in new rings and a piston and see if this fixes my problem? What do you guys suggest?

Thanks in advance.

New rings in a worn cylinder is a recipe for disaster. Best to bore the cylinder and replace piston, rings and rod. Should run less than $300 if you do all but the machine work yourself. Or, contact J-Mech here on this forum and see if he'll rebuild it for you.

exactly what you get with a cheap rebuild. round rings in a oval bore don't seal real well

I mistyped earlier, I shouldn't have said the cylinder was out of spec, but rather it was out from new spec. Which is to be expected. It is still within the max wear limit, out of round, and taper. The wear is almost between 3.752 and 3.7525, out of round was about 1.5 thou and taper was almost 1 thou.

Anyways, tore the piston out tonight to investigate further. There was some gray mud in the bottom of the pan, crank journal looked find as did the rod. Upon pulling the piston and rod, the top ring fell out of the piston in 4 pieces (2 large pieces and 2 about 1/2"), the second ring came in 2 (one large and the second was about 3/8"). I'm unsure what would cause this. There is no major scoring or gouges in the cylinder. Piston skirt was were wearing pretty bad, as to be expected and would also explain the grey mud in the pan.

Any ideas what would cause the rings to break?

The piston does not appear to be any of the kohler pistons as described in the service manual. It is closest to style C with the recesses on the pin ends but does not have the raised cross thatch marks. I'm wondering if this was a cheaper/knock off piston and ring set that just didn't hold up?

Sounds like what happened to the k241 in my 108. Took the engine to the dealer to rebuild. The just re-ringed it, said it didn't need boring. Well, it lasted about 20 hours until it behaved just as you described yours. I pulled the piston, had the grey sludge in the crankcase (aluminum) and worn piston skirt. Took it back to the dealer, he had it bored .010 over and rebuilt gratis.

Since that experience, I've rebuilt them myself--less the actual machining. If you want something done right...as the saying goes.

If the ring end gap is too tight, when it gets warm the ends will butt and break the ring. Seen it happen on race engines with file fit rings. Not sure if it's your problem, but it's the first thing that came to mind.

I'm thinking the ring gap could have been the issue. Of course I can't measure them now. Also, not sure if the knocking from the timing or the timing it's self being off would cause it either. But the gap issue could explain both rings broken so close to the cut in the ring. I'd think if they were cracked on install it would have been somewhere not right next to the cut.

I don't believe the cylinder is that far worn to warrant a bore job, not in my opinion. Also checked with my father who was a GM cert. mechanic back in his day, and has worked on everything from chainsaws to diesels and he also doesn't think that this would need bored out. Not saying you guys are wrong but at this point in time I'm going to try my luck with a new piston and rings and see how I make out. The overall condition inside the motor is pretty good and doesn't show much wear anywhere. The meter shows just over 300 hrs on it. So I'm thinking this tractor has had a pretty easy life.

Ring end gap should be .010/.020. I would set it half way down the cylinder.

You can also check the cylinder for taper by checking the ring gap at the top and bottom of the bore.

Good point about the taper. I will double check it when setting the gap. Looks like the parts should be here by the weekend so hopefully should be running again next week.

If you have silver sludge in the crankcase and worn piston skirts, I think the knocking you heard was probably piston slap.

FYI, my k241's cylinder was within spec, too.

I think you are wasting your time not boring the cylinder.

But, it is your tractor.