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Engine Knocking


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02-13-03, 04:10 AM   #1  
Kohler Knocking

Hello, everyone. Hopefully I can get some advice here. I rebuilt a Kohler K241 10hp a couple of months ago; new piston, rings, rod, and valves. The cylinder was dingle-balled, it was not out-of-round or scratched up, and the crank checked out OK also. The piston and rod that I bought are the original size. The valve seats were ground. Everything was lubed very well when it was put together. I had some help from a friend who has rebuilt a few of them, and he also did the work on the valve seats and bore (him and his father have a complete machine shop.)

I did make one mistake when putting it together, the breaker cam was put in 180 degrees out, so it did have to be torn back down to correct this (crank and piston came back out). The connecting rod I bought had the posi-lock nuts on it, and these were tightened to 200 in-lbs the second time it was installed.

It had run fine until yesterday. I ran it for about an hour after the rebuild, driving it around the street and yard to get some time on it, varying the rpm's, and then changed the oil. Since then, I've got about 10 hours on it, doing some light snow plowing, all in low gear. Last night, it started knocking real good, and sounds like I might be where I was before the rebuild.

My questions are: What could be a cause of this? Do you think the rod was put together incorrectly? I've heard some say you shouldn't re-use the posi-lock nuts. Should I get the crank turned, and buy an undersize rod? As I said, the machine work would not cost anything, it's all available.

Thanks for any help!

Jeff

 
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02-13-03, 08:06 PM   #2  
mikejmerritt
Hello NotMrWizard, I could only speculate what may have happened that led to the knocking after your rebuild. Rod cap on reversed, grain of dirt or many other things. I have re-used posi lock many times with no problems. Did you check the end play in the crank? This is fairly critical for proper break in.
Since machine work is free and you need another rod go with the -.020 rod. Get that end play spec right also.....Mike

 
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02-13-03, 09:29 PM   #3  
Hello Jeff!

I agree with Mike. Check the rod journal size with a micrometer. If it is out of spec, get it turned. There's not much speculating about what really happened until you get it back apart and find where it is knocking. Is there a chance the pulley came loose on the crankshaft? That has fooled me a time or two when all of a sudden an engine starts knocking. Every time the engine hits, it bangs the pulley at the keyway notch, making a knock. Loose engine mounting bolts will do this too.

Otherwise, tear back into it and let us know what you find.


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02-15-03, 05:56 AM   #4  
Have you considered a valve lifter. I know, on the newer Kohlers the valve lifters can be noisy if they get the wrong oil wieght.
I have not worked on a Kohler is old. It may not have hydraulic valve lifters.

 
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02-15-03, 06:41 PM   #5  
Well, got it taken apart ... flywheel wasn't loose, neither was the pulley. Drained the oil, it didn't look bad, no chunks of metal or foreign objects. There was some "streaking" in the oil when I dragged my finger through it, I attribute this to the rings wearing in. Pulled the head off, no scratches inside the cylinder. Everything looked OK inside, oil hole in the rod cap facing the correct way, looks like oil's been getting splashed up real well. The nuts on the rod cap were not loose (which I was thinking that would be the problem), so I pulled it off. Inside of the cap looks good, no major scratches except for one faint wear line in it. Is this normal? The cam end play is within spec, I didn't check the crank end yet.

I'm going to mic the crank tomorrow. I guess my question now is, if the journal is in spec, along with the ends, what should I look for next? I'm kinda stumped here. I figured the rod size is good since it was new. Maybe it could very well be piston slap? I just ruled this out due to the knocking during cranking. I've had 5W-30 oil in it, I figured I should be OK there.

Thanks for the help!

Jeff

 
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02-15-03, 08:18 PM   #6  
mikejmerritt
When you check the crank mic it both ways to check for out of round. I would be interested to know what the crank journal mics to.
Did you happen to check the crank end play before you took it down. If you have to much or not enough it can be hard on the engine.....Mike

 
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02-18-03, 06:46 AM   #7  
I've been out of town for a few days, haven't had a chance to check things out, but hopefully I will tonight. Thankfully, the 7" of snow that was forecasted for Friday night never materialized!!

I was also going to plastiguage the rod/crank if the crank checks out OK. If I do this, should I torque the posi-lok rod bolts to 260 in-lb or to 200 in-lb? The directions that came with it stated 260 in-lb and not to reuse them, I've found specs that state you can reuse them with a torque of 200, and I've had some DIY'ers say torque it down to 265-270 in-lbs.

I'm also going to check the crank end play. It sure doesn't seem to move more than .010", and is pretty hard to do at that. The rod has about .010-.012" end play on the crank.

Thanks for the help, and I'll be sure to post the results.

Jeff

 
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02-20-03, 05:25 PM   #8  
First of all … man this is a great website for people helping you out! Thanks, all!! So here’s the story … remember this was a honed cylinder, same crank, new standard sized rod and piston. I’ll start with the cylinder bore. Diameter is 3.253” (spec 3.254” wear limit). The cylinder has vertical wear marks on the sides of the cylinder that are in-line with the crank centerline. No deep scratches, no ridge at the top of the cylinder.

The piston has vertical wear marks that are on the same sides as the conn rod bolts. There also is some scuffing (shiny spots) at the very bottom of the piston skirt at these marks, and right underneath the first oil ring. Piston ring end gap on the old rings when installed in the cylinder was .024” (spec .010-.030”). End gap on the new rings was over .035” (spec .030” max)!! How can this be?? The rings were ordered with the piston as an assembly!

The connecting rod-to-crank running clearance was plastigauged, and is .003” (spec is .0025” max). End play on the crank is .004” (spec .003-.020”).

Camshaft end play is .007” (.005-.010”).

Now my questions are … do the shiny areas on the piston mean there is piston slap? Will the oversize running clearance on the crank create the knock I am hearing? I’m curious that the wear lines on the piston are 90 degrees from the wear lines in the cylinder. I’m also concerned with the ring end gap. I’m almost tempted to bore the block, buy a .010 over piston and rings, and turn the crank .010 under and buy a new undersize rod.

Sorry this is kinda long, and thanks for all the help!!!

 
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02-20-03, 07:45 PM   #9  
Well, it sounds like you're dealing with an engine that is on the border of being "worn out", so it wouldn't hurt to go ahead and machine it. I don't think that the rod clearance is what you are hearing though. I think you have some piston slap, like you suspected, because of the wear pattern that you described. Did you check the wrist pin clearances?

Was the replacement piston assembly stock or aftermarket? I have run into some new rings that had bad end gaps too. Is there any chance that this engine has been re-ringed before? Maybe someone installed .010 over rings in it and filed them to the correct end gap to compensate for cylinder wear.


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02-21-03, 06:55 AM   #10  
Cheese, I'm not sure if the replacement piston was stock or not. I used an online parts supplier. I went this route due to the price difference from the local dealer ($37 for the piston compared to $100 at the dealer!). Problems with that, maybe? I'm not sure if the engine had been reworked or re-ringedin the past, I know it hadn't been bored.

Thanks!
Jeff

 
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02-21-03, 07:29 PM   #11  
Probably aftermarket for that kind of price. Definitely if it wasn't in a Kohler marked box.

Lots of times people install oversized rings, and file or grind the ends until they get the proper fit when they are dealing with a worn out bore. (and they don't want to get into a full re-build).


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02-23-03, 11:52 AM   #12  
Well, let's file this one under the "lessons learned" category. The crank is right at the wear limit, so I'm getting it ground, but more importantly, I had the wrong piston!! I don't know what it is for, but it's definitely not for this engine! I did not double check it when I received it. Called the supplier, and they are getting it replaced. They were very apologetic and helpful. So ... got a new piston, rod, and head gasket coming. I'm hoping this will do it! I'm surprised it ran as long as it did with that piston.

Thanks to all who offered advice on this one!

Jeff

 
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02-23-03, 05:46 PM   #13  
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Hi Jeff, I think I might be able to lend a hand or at least try. When I rebuild a Cast iron K series at our shop we make it a rule to use only Kohler parts. Don't get me wrong,I know they are expensive, but they are well worth the investment. First off, you have to be careful with your crankshaft. Your Kohler K241 10hp crankshaft has a maximum undersize grind limit of .010. It is very critical that the oil hole in the rod cap face the camshaft for proper oiling. Maximum bore limits are .030 for the cylinder. I've seen a lot of people rebuild their kohlers and end up purchasing a shortblock because the did not purchase a Kohler service manual when rebuilding and sent the rod flying across the front lawn. If you give me the spec number on your Kohler I can get you all the proper Kohler part numbers you need.
Josh

 
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03-20-03, 08:23 PM   #14  
Ok. I need help before I pull out what's left of my hair! I got this thing put all back together, everything torqued correctly, rod on the correct way, everything was checked and double checked while doing it. Everything was lubed up really well, poured about a teaspoon of oil on top of the piston, made sure it was lubed up well, go to start it up ... cranked a few times, started up, ran about 10 seconds, and started knocking!!! What in the world am I doing wrong??? The bore was checked with bore mics, got the correct parts, I'm at a loss!! New key on the crank, the flywheel is not loose, used Kohler parts ...

Anybody got any ideas??

 
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03-20-03, 10:07 PM   #15  
Are you using pre-lube or assembly lube when you put this thig together? Not grease or oil for pre-lube, right? Did you check the symmetry of the cylinder to be sure it is not out of round? (with a mic). End play on the crank? Has the head been shaved? Does the piston rise above the block deck at TDC? Is there any chance that the engine may be loosely mounted, causing the knock sound?

Things like this happen every once in a while. Sometimes the simplest of jobs end up taking 10 times the amount of time to get it right due to some freak or unordinary flaw or problem. It becomes a vendetta to me, and I refuse to let a small engine "beat me", so I keep on until I find the problem. The case may be the same here. Go back over EVERYTHING you did in your mind, from top to botttom and start to finish. Pull the head and/or sump cover if you need to to determine the source of the knock. Rock the flywheel back and forth in different spots while feeling and listening for play.


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God bless!

 
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03-21-03, 09:25 AM   #16  
I used oil for lubing everything inside when I put it together, not pre-lube. Is that recommended? Cylinder was checked out, diameter at 3 depths and again at 90 degrees, pistong doesn't rise above the deck, head hasn't been ground, dipper on the rod is the same length as what was originally in it, and mounting bolts are tight. If I pull the head, do I need to replace the gasket, or can it be reused (the metal-style gasket)? Rotating the flywheel around by hand does not produce any noise/hitting/knocking. It's nice and smooth all the way.

Like you, Cheese, I REFUSE to get beat by a 40 yr old 1-cylinder engine!! Lol! But now it's getting to be lawn-rolling time!

Thanks!
Jeff

 
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03-21-03, 04:56 PM   #17  
A little more info - took the carb off and the valve cover. No broken springs. When the piston is at TDC, I can rock the flywheel back and forth, and hear something inside the engine knocking. It sounds like it's coming from the cam side of the engine, kinda hard to tell with the shrouding on and all. When I'm on either side of the tractor, it sounds like it's coming from the other side. Any ideas? I will hear the knock both ways, when the piston starts going down or up.

Also, I seem to have lost spark. Cranks good, but there is a very weak (or nonexistent) spark when I ground the plug electrode against the block. All the wires are OK, could it be the condenser got fried? How do I test it?

Thanks, everyone!

Jeff

 
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03-21-03, 05:48 PM   #18  
A bit more info ... got the head off, when the piston is at TDC, and both valves are closed, this is where I hear it. Pushing against the piston, I couldn't feel anything. But I could when I pushed against the valves. If I hold both valves open with a screwdriver, I won't hear anything. It's almost like the cam lobes are whacking the valves. This engine is the 2-piece cam with the compression release lobes. I can hear them moving around when I rotate the crank.

 
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03-22-03, 12:58 AM   #19  
Not sure, but I think you may have a problem with the cam journals. With the pressure of the valve springs holding the lifters down on the cam, rocking it between lobes on the cam would tend to place pressure on the cam from different angles. If the cam journals were worn, it would allow the cam to "rock" a little.

I don't think you should be able to hear the flyweights on the compression release either.

Check your ignition components. If the points look good and the gap is right, but you still have a weak spark, then the condenser is probably at fault.


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03-23-03, 05:30 PM   #20  
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Does your Kohler 10hp have a 12volt ignition, magneto under the flywheel or Electronic iginition with a pick-up coil mounted on the left hand side of the flywheel? Did you use plastigauge on the crankshaft and the rod before assembly to check for proper clearance? It is extremely rare for a K24

 
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03-23-03, 05:30 PM   #21  
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Does your Kohler 10hp have a 12volt ignition, magneto under the flywheel or Electronic iginition with a pick-up coil mounted on the left hand side of the flywheel? Did you use plastigauge on the crankshaft and the rod before assembly to check for proper clearance? It is extremely rare for a K24

 
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03-24-03, 04:04 AM   #22  
It's definitely in the valve train and not the crank or rod. Only happens between the exhaust and intake stroke, when one valve is opening and the other is closing. I'm tending to think it's the cam. I think I'm going to open it up all the way, and see if I can tell if the tappets (I think that's what they are called) are losing contact with the cam. Do the new 1-piece cams still have the compression release function?

No magneto under the flywheel, it's electronic ignition with the coil mounted on the right side of the engine.

Thanks!

 
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04-14-03, 10:12 AM   #23  
Well, I finally had a chance to get back to this guy, thought I'd let you know what I found out. Ended up taking the engine to a local Kohler expert to have a look-see. I figure if he's worked on them for 30+ years, he can figure it out! He took out the crank, cam, and valves. Checked all the specs. The only thing he found was the crank end-play was on the low side, between .004-.005" (same thing I found also). Spec is .003-.020". The only thing he did was put in another shim for the crank, and button it back up. It's been sounding good for 8-10 hours now. Maybe that's all it was. He wasn't too concerned with the slight knocking when rocking the flywheel back and forth, said he's also seen that and that wasn't causing the hard knock. I guess if it ever starts again, I'm going to load up the tractor and take it to him to listen to.

Thanks to all those who helped me out on this!

 
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04-14-03, 09:44 PM   #24  
Good deal...I was beginning to wonder what in the world could be wrong with it. Glad you got it fixed!


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