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.

I hope this works out for you but statisticly it doesn't. Old cast iron Kohlers don't
usually don't respond well to a ring and hone job. I've only tried once and it didn't.

If the piston was slapping why would adjusting the valves, points, and plug gap eliminate it? It was a very definitive knocking before I adjusted those three and afterwards had no knock at all. It would also spudder and hesitate and not come up on idle fast before adjusting it. All those symptoms also disappeared after the adjustments were made.

If it were piston slap wouldn't the knocking still have been happening when I used it for close to an hour?

The fact that you have silver sludge in the crankcase is proof of piston skirt wear.That is caused by piston skirt rubbing the cylinder wall. Usually most noticeable under heavy load. Whether and under what conditions you hear it may vary. Poor timing by itself does not cause that kind of wear but a loose piston in an oval cylinder will suffer from poor timing more dramatically.

You started off this thread with "PO put new piston and rings in..." Now you are about to repeat his mistake.

What's the definition of insanity? Doing the same thing repeatedly and expecting a different outcome...

Not saying you are insane, don't take offense. Just sayin' you're in denial.

All that being said, if I were not building the machine for long term work, maybe just tooling around with a cart or something, that didn't stress the engine, you might be able to run it for a number of years with just a ring job. But to cut grass, plow, snowblow, think about the time you'll have invested and the long term payback of a fresh engine. We've all made the mistake you are contemplating.

Well, you came here with a story and asked some questions. Now your arguing with those answers.

It's a waste of time to put pistons and rings in it, but it's your money and your motor.

Yep, you probably had a spark knock and it went away.

I question your measurements because you gave them, then said you pulled the piston. You can't measure taper with the piston in the hole. Do you have a bore gauge? Inside mic? Or are you using a t-bar and a cheap caliper? If you do in fact have the measuring tools to get a good check on the bore, you are either an experienced mechanic, or a machinist. If your using questionable methods, and cheap tools, then your jerking us around with the numbers. Which is it?

Glad your dad worked for GM. How many Kohlers has he rebuilt? How many motors? Most all factory trained techs I've interviewed seldom ever saw the inside of a motor because a dealer just replaces, never rebuilds. I've rebuilt hundreds of motors, and I'm telling you your wasting your time. I have this feeling your going to argue with me too......


EDIT: More than likely, it is an aftermarket piston in standard bore. The skirt clearance was probable too tight.... and you going to try that again???

:popcorn::popcorn:

Same experience with one, did the rest the right way

35 years ago, my boss gave me his 104 and told me he wanted it fixed. Was burning oil and low on power. Fix it cheap he said!

I got it apart and saw the piston top was eaten away almost down to the top compression ring. The bore looked good as far as wear. I didn't measure it except eyeball. New Kohler piston and a set of rings and back together. No valve job, just piston and rings.

That was 35 years ago and the thing ran for him for another three years then he sold it to me after the sediment bulb filled up with water and wouldn't run. I used it for ten years and it's basically been parked since but still running okay. No telling how many 100's of hours is on that little engine because he had a very large yard and he cut his dad's yard and his sister's yard down on the farm with that thing.

I guess you can get lucky now and then but WDIK? I'm not certified on anything!

:biggrin2:

I believe what Mike says is exactly right, once in awhile you can get lucky.

I bet he feels like one in a thousand, maybe one in ten thousand...

My question to the OP is, why do you think you can do the same thing that a PO did and end up with a great machine when the PO couldn't do it?

The op asked for opinions, and mine is: Someone already tried the cheap fix first and the only person it worked out well for was the guy who "unloaded it".

Fix it right and use it, or do the same thing that someone else already tried and failed at.

The OP doesn't need to justify anything with anyone here, he asked for opinions, not debate.

I don't feel that a rebore is needed if the cylinder is truely within spec. A bad hone job will also cause ring seating issues. I think it is false to say every engine needs to be bored to be considered rebuild properly.

I do agree that most of these engines that get torn down probably do have out of spec cylinders that need to be machined.

The statements above are only my opinion. Please don't beat me up to bad for stating it.

Measure the cylinder in 6 places like the Kohler manual says and report back with your findings.

You also need to post what tools you used to measure the cylinder.

One thing you need to remember when rebuilding/replacing a piston and is the cylinder will grow in diameter when you hone it. I've been a machinist for close to 40 years and saw enough poorly done rebuilds that I could write a book.

The silver sludge in the pan is another indicator that the motor needs some major work done to it. I would recommend you check the crank pin and rod journal to make sure they are in spec. Crank pin should check in 6 places per Kohler manual.

You also need to post what tools you used to measure the crank.

Clearly some of you have the wrong impression here. I've not shown up here to argue with anyone, nor have I began to argue at all. If you took my questions as arguments then you're mistaken and please forgive me for asking questions that some may think are obvious enough to consider it an argument.

And several of you are correct. I came here asking for opinions and trying to learn about this engine. I received all your opinions openly and, even if it seemed like it, have not argued with any of you. I trust your knowledge and appreciate you offering assistance.

I did, in fact, decide to order factory standard sized parts to put back in it. I hope for my wallet and time that it works out. You all can hope what you will. If it fails within the next several hours of running on the new piston I will return to tell those of you out there that you were correct.

Thank you to those that were helpful.

Rendrog18, I truly hope it works out OK for you. After all, only you can make the decision on what to do with your engine.

I agree you have not been argumentative, and by no means are you obligated to follow any advice given here. Some of us have strong opinions, and in our fervor to save someone from mistakes we have made, may come across as too pushy. Be assured that we are all friends here, and welcome you and others that may venture into the world of Cub Cadet collecting and restoring.

Post some pics of your rebuild, and some of the measurements that Merk suggested. We will all learn from your efforts.

Above all else, keep a sense of humor about this. It's supposed to be a fun and rewarding hobby. :beerchug:

Well said :beerchug: