Kohler k301s knock sometimes

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   I have a Kohler k301s out of a Allis Chalmers 912H and I just got it running again after I put a new crankshaft and new connecting rod and piston rings in it and there is a knock after it gets hot but it only does it here and there. It goes away at full throttle and at lick half throttle then comes back after a little run time. I idle it back down and it runs fine for about 15 seconds then knocks again. Anyone have any ideas?

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AllisChalmers912 Members Profile Send Private Message Find Members Posts Add to Buddy List Bronze Level Joined: 30 Mar 2026 Location: Middleburg PA Points: 6	Post Options Post Reply Quote AllisChalmers912 Report Post Thanks(0) Quote Reply Topic: Kohler k301s knock sometimes Posted: 30 Mar 2026 at 6:36pm
	I have a Kohler k301s out of a Allis Chalmers 912H and I just got it running again after I put a new crankshaft and new connecting rod and piston rings in it and there is a knock after it gets hot but it only does it here and there. It goes away at full throttle and at lick half throttle then comes back after a little run time. I idle it back down and it runs fine for about 15 seconds then knocks again. Anyone have any ideas?

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DaveKamp Members Profile Send Private Message Find Members Posts Add to Buddy List Orange Level Access Joined: 12 Apr 2010 Location: LeClaire, Ia Points: 6124	Post Options Post Reply Quote DaveKamp Report Post Thanks(0) Quote Reply Posted: 30 Mar 2026 at 11:42pm
	First and foremost, make ABSOLUTE CERTAIN that your flywheel is NOT LOOSE. They can feel tight, and still wander, and sometimes they'll develop a totally invisible internal crack, that under the right conditions, will expand and release force in the taper. In MOST cases, the cast iron flywheel will stay together fine under 'normal' engine governance, but I've had one that had an invisible crack open up at a 'slightly above factory governed speed' once, and I caught it before it came apart... The K301 had balance weights (balance gears) that spun opposite to crankshaft direction to counteract primary imbalance. They need to be shimmed and timed properly on assembly, and if they've got wear, they'll be sloppy. When these gears aren't done right... and sometimes when they are, the'll come unglued and go on a lateral vacation, leaving a picture window in the block. Usually, the warning is a rattle or knock at low speed/partial load or idle. Most likely NOT spark knock, although these flatheads WILL, given enough of a load. air-cooled flatheads develop hot spots pretty easily... but what you describe just doesn't sound like preignition to me.
	Ten Amendments, Ten Commandments, and one Golden Rule solve most every problem. Citrus hand-cleaner with Pumice does the rest.

AllisChalmers912 Members Profile Send Private Message Find Members Posts Add to Buddy List Bronze Level Joined: 30 Mar 2026 Location: Middleburg PA Points: 6	Post Options Post Reply Quote AllisChalmers912 Report Post Thanks(0) Quote Reply Posted: 20 hours 41 minutes ago at 5:38am
	Thank you for the answer Dave. We are going to look at the valves today and if we see nothing wrong we are going to tear it down again and look at the balance gears and see if we can find what the issue is. We may even take a good look at the flywheel to see if it is cracked.

DrAllis Members Profile Send Private Message Find Members Posts Add to Buddy List Orange Level Access Joined: 12 Sep 2009 Points: 22804	Post Options Post Reply Quote DrAllis Report Post Thanks(0) Quote Reply Posted: 14 hours 28 minutes ago at 11:51am
	What was the piston skirt clearance ??? Back when those 914's were new, Kohler was selling so many engines to people, they couldn't keep up. As a result, many blocks weren't given the customary "X" amount of days cure time before the blocks got bored. Then, when the engine got to be 2 or 3 years old the cylinder bores weren't even straight and had to be bored oversized for a new piston that fit correctly in a straight and round bore.

AllisChalmers912 Members Profile Send Private Message Find Members Posts Add to Buddy List Bronze Level Joined: 30 Mar 2026 Location: Middleburg PA Points: 6	Post Options Post Reply Quote AllisChalmers912 Report Post Thanks(0) Quote Reply Posted: 13 hours 54 minutes ago at 12:25pm
	DrAllis, I do not remember off the top of my head what it was.

DrAllis Members Profile Send Private Message Find Members Posts Add to Buddy List Orange Level Access Joined: 12 Sep 2009 Points: 22804	Post Options Post Reply Quote DrAllis Report Post Thanks(0) Quote Reply Posted: 12 hours 30 minutes ago at 1:49pm
	Was this your engine and it was a runner and you tore it down and did all this work to it??? Or is this something you picked up and have never heard it run before ??? and I'm taking it that you did not bore it and install a new oversize piston ??

AllisChalmers912 Members Profile Send Private Message Find Members Posts Add to Buddy List Bronze Level Joined: 30 Mar 2026 Location: Middleburg PA Points: 6	Post Options Post Reply Quote AllisChalmers912 Report Post Thanks(0) Quote Reply Posted: 12 hours 4 minutes ago at 2:15pm
	My pap got it for free from one of his neighbors that he was helping doing so work for. He got the tractor with the engine blown up with the connecting rod destroyed and the crankshaft scored bad.

Coke-in-MN Members Profile Send Private Message Find Members Posts Add to Buddy List Orange Level Access Joined: 12 Sep 2009 Location: Afton MN Points: 42266	Post Options Post Reply Quote Coke-in-MN Report Post Thanks(0) Quote Reply Posted: 6 hours 45 minutes ago at 7:34pm
	Have 2 K341 - 16 HP engines out of my New Holland S16 - Over the years have rebuilt both , bore , new crank , and last time I had a balance gear brake and take the dipper off new rod I just put in - The S16 now has a Honda engine in it , I have given up on Kohlers
	Life lesson: If you’re being chased by a lion, you’re on a horse, to the left of you is a giraffe and on the right is a unicorn, what do you do? You stop drinking and get off the carousel.

AllisChalmers912 Members Profile Send Private Message Find Members Posts Add to Buddy List Bronze Level Joined: 30 Mar 2026 Location: Middleburg PA Points: 6	Post Options Post Reply Quote AllisChalmers912 Report Post Thanks(0) Quote Reply Posted: 6 hours 38 minutes ago at 7:41pm
	We just took the engine apart tonight and someone along the 40 some years took the balance gears out of the engine so we have ruled that out and the only thing we can think of without taking it fully apart is the piston slap, everything looks fine and my dad tried to wiggle the piston back and forth from the bottom side so we dont know what the issue is, we are just going to put it back together and if something happens, then we will just deal with it. It also has a .020 over piston so someone has also bored it out also along the line. Edited by AllisChalmers912 - 6 hours 37 minutes ago at 7:42pm

HudCo Members Profile Send Private Message Find Members Posts Add to Buddy List Orange Level Joined: 29 Jan 2013 Location: Plymouth Utah Points: 4070	Post Options Post Reply Quote HudCo Report Post Thanks(0) Quote Reply Posted: 3 hours 37 minutes ago at 10:42pm
	i think the 12hp had balance gears 14s and 16 had balance gears but they run fine without them you could be pinging a little change the points gap a little bit its one cylinder so it will change your timing just a little

55allis Members Profile Send Private Message Find Members Posts Add to Buddy List Orange Level Joined: 30 Jun 2020 Location: Griswold Iowa Points: 1339	Post Options Post Reply Quote 55allis Report Post Thanks(0) Quote Reply Posted: 3 hours 11 minutes ago at 11:08pm
	What kind of gas do you run? Ethanol or premium gas? Mine run hot and developed a slight knock if I run too much ethanol in them. Even if the head had been shaved will cause some compression knock sometimes, have that on a 14hp kohler I rebuilt. I have been removing the balancer gears in all of mine due to them having problems unless they run good without any knock or funny noises. Love kohlers, have been very reliable for me.
	1955 AC WD45 diesel with D262 repower, 1949 AC WD, 1963 A-C D17 series 3, several Allis garden tractors