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Machinery enthusiast
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Discussion Starter #1
I resently put a new piston, rings and rod in a K181S and also cleaned up and lapped the original valves. The cylinder looked good so no overbore was done. New breather, gaslets, seals, points, plug and condenser rounded out the repair. The engine starts immeditely and seems to make more power than I could recall. But it had this annoying knock at all rpm except idle and wot under load.
After approx 10 hrs of this I took it back down expecting to see cracks in the piston etc but found no problems. Everything looked great and was still within specs. Having found nothing wrong and/or out of spec I put it back together and while I had it on the bench I reset the points as it was way easier to get at them. With no doubt in my mind I had them set to .020, back the engine went into my trusty 66 Wheel Horse 856.
Well the knock was still there but at all rpm now. Hummm, seems I made it worse.....
I did alittle reading up on the Kohler engine and found the correct proceedure to use for setting the timing. Timing? I've never knowingly set the timing on that old K181 before and I"ve owned and serviced it for over 20 yrs!
Following Brian Millers well written instructions I went at the timing.
Long story short, .020 is way too advanced but it will get the engine going.
On the K181 there is a plug on the back of the bearing plate and when removed the flat edge on the backside of the flywheel is easily seen. The mark I was looking for was the "S" mark on this edge. When the timing is correct the "S" should be centered in the hole at idle. Using a std automtive timing light, the "S" was no where in site. Slowly adjusting the points at idle closed "retarded" the timing enough to where the "S" became clearly visable and I looked the points down. Be advised that the points may slightly expand when tightning down so take that in consideration when setting them.
The static setting of the points are now .018 and it runs quieter, starts easy and seems to have more power and the best news is the knock has practically disappeared. The slight knock I hear now I'll attribute to the piston being stock size and not .003 over size.....
In closing, those that may have knocking and/or peformance problems w/ their K engine should include a timing check. It could be the problem.

fyi, the timing marks and locations differ on each K engine so it could be very easy or very hard to get to.
Good luck
 

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Moderator
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Thanks for the info--my friend....:D
Brian Miller seems to be very accomplished in his versitility and understanding of these Kohler -"K"'s...
 

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Collector of many tractors
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15,265 Posts
Two things... The knock could be piston slap at the bottom of the bore... The way to check this is to turn the engine over until the piston is all the way down and then see if you can rock it by pushing on the top of the piston... If it rocks then this is what you here...
The second thing is the crank moving in and out slapping the side of the case... You can check this by holding a wood board tight against the side of the crank so it cant move when its running and start it up to see if the knock went away..
 

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Yup--end thrust knock is often mistaken for a rod or piston noise..I have a few Tecumsehs that sound bad but its just a bit of excessive end play in the crank..dont forget todays alcohol laced gasoline isn't what was around when that Kohler was born too--they had higher octane leaded fuel back then..but a book I have on making your own alcohol fuels claims the timing needs to be advanced when using alcohol,more than it would be on gasoline..I would think alcohol would be more likely to detonate or cause "pinging" than gas,but advancing the timing would worsen that,not help!..

I'd just ensure the flywheel is tight,and run it,if you see no apparent wear or damage going on,myself..I had one engine I ran 20 minutes with a "weird knock" and it turned out the flywheel nut loosened,and it ATE the tapered part of the crank & flywheel BAD,the keyway slot went from 3/16" to more like 1/2"!..I was surprised it still ran decent,you'd think the timing would be so far off it would have stalled,but it didn't..
 

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Machinery enthusiast
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4,257 Posts
Discussion Starter #5
Good suggestions. When I had it down I tried to rock the piston and couldn' get it to rock. Those new rings must have tightened it up considerably.
re. crankshaft endplay, from when I did the original rebuild (post # 235 back in 2007):
Good news is that it was what I hoped. Long story short, I shoulda checked the crankshaft end play when I had it down the 1st time and since I didn't she had to go under the knife again.
Specs call for no more than .023" in crankshaft end play and what I had was more than my .035" feeler gauge could measure, perhaps 1/32" maybe. In any case I could move the crankshaft in and out more than what is allowed and as the load (rpm) increased the more the crank would bang around in it's main bearings. Amazingly it hasn't damaged anything in the many yrs it's been doing it......
The fix is to remove or add shim gaskets between the bearing plate and block to get the correct clearance. The rebuild kit I got had 5 .005" gasket shims and one thick gasket shim (perhaps .020").
pic 1, flywheel & bearing plate removed.
pic 2, the main bearing looked and felt real good, No need to replace.
pic 3, new oil seal installed on bearing plate.
pic 4, shimming the bearing plate. I ended up using 3 .005" gasket shims to get .004" clearance which is well within the .002 - .023 specs.
Had to butcher up the pan gasket so reassembly awaits a new gasket. Oh well, atleast the piston, rod and what I could see of the cylinder looked pretty good....
http://mytractorforum.com/attachment.php?attachmentid=26926&d=1188871344
 
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