PPGman 5 #1 Posted June 18, 2010 Just finished up my C-120 restoration a few weeks ago, new piston, rings, valve job.....everything went together nice and according to specs. Engine is a kohler 12hp. Was mowing with my tractor monday, started to notice a slight knock. Engine runs great, but the knock/ engine noise has progressivly got worse. Took the tractor to the garage and noticed there was oil pushing out the governer....not much, maybe lost a few ounces. Pulled the dipstick, it was still reading a smudge below full. Started looking and pulled the breather apart....grabed the kohler manual and it was indeed not installed correct. I reinstalled it correctly, slapped the carb on, and i had indeed stopped the oil leak out the governer....but, still had the engine noise. Sounds alot like a knock. Played with the timing, checked the valve clearence....everything was on the money. This morning, i tore the head off expecting to see a mess..., and to my surprise, everything looked good. No evidence of anything rapping off the head. There was maybe a few drops of oil sitting on top of the piston, but i didn't see anything that looked like a grenade went off on the top end of this motor by any means. ( Could this oil be part of the breather not installed correctly?) Not seeing anything that looked like huge issue, i pulled the engine so i could get at the oil pan. Pulled the pan off, spun the motor around, and there was no play in the rod, or cap. I took the cap off the rod, and everything looked good. I started messing around shaking and pulling everything and noticed the front balance gear was loose...it actually wobbled. I reached back in and found the one in the rear, and it was looser yet. Can i take these gears off and get rid of them?? The front gear looks like i could get it off with little problem....but the one in the rear looks pretty tight. Does anyone know if you can get the rear balancer off without pulling the crank?? Could this be where my noise was comming from?? Any insights or thoughts would be a big help.....i'm still scratching my head here trying to figure out this noise. Thanks :D Share this post Link to post Share on other sites
TT-(Moderator) 1,128 #2 Posted June 18, 2010 If you haven't already conquered this....... These engines are "zero balanced" and do not rely on the DCB gears to keep them from shaking themselves apart. Although they do help with the "thump" typical of a large single-cylinder engine as the crankshaft counterweights swing and the piston assembly changes direction rapidly, they are not necessary for operation. You can pull the bottom gear off by removing the snap ring. As for the top gear...... split it with a cold chisel and it will come right off. Throw all the pieces in the trash and don't look back. :D Share this post Link to post Share on other sites
oldandred 15 #3 Posted June 18, 2010 one question did you have the block checked to be sure its not out of round the cyl, wall look at the piston if its out if its out of round you will see wear on one side thats were the piston rocks back and fourth in the cyl, and will sound like knock Share this post Link to post Share on other sites
WH nut 553 #4 Posted June 19, 2010 You did put the rod on right didnt you, Oil hole towards the cam Share this post Link to post Share on other sites
PPGman 5 #5 Posted June 19, 2010 one question did you have the block checked to be sure its not out of round the cyl, wall look at the piston if its out if its out of round you will see wear on one side thats were the piston rocks back and fourth in the cyl, and will sound like knock I'm confident that the cylinder is in good shape. It measured well from top to bottom, and it was in specs for a standard piston when i did the initial rebuild. When i pulled the head off, there was no indication that anything was wearing improperly. Not a mark on the cylinder head, the piston looked good, no wear marks on the bore nor the piston. The only movement i could find was in the balancer gears in the bottom end. Share this post Link to post Share on other sites
PPGman 5 #6 Posted June 19, 2010 You did put the rod on right didnt you, Oil hole towards the cam humm.....had me thinking there for a min. Just checked to make sure, and yes the oil hole is correct. Share this post Link to post Share on other sites
PPGman 5 #7 Posted June 19, 2010 If you haven't already conquered this....... These engines are "zero balanced" and do not rely on the DCB gears to keep them from shaking themselves apart. Although they do help with the "thump" typical of a large single-cylinder engine as the crankshaft counterweights swing and the piston assembly changes direction rapidly, they are not necessary for operation. You can pull the bottom gear off by removing the snap ring. As for the top gear...... split it with a cold chisel and it will come right off. Throw all the pieces in the trash and don't look back. Terry, i got the bottom gear off with no problem the other night. The back gear took me about 30mins to finally grab the snap ring, but i can't get it off. Ohhh...its so close, but whichever way i turn the crank, its not enough to clear the pin. I was actually thinking about trying to split it with a chisel as well, but kept having bad visions of that pin splitting the case when i gave it a good shot. You think it would split with little trouble?? What would be less risky of damaging my block......splitting the gear, or trying to drive the pin? If i drive the pin....than i got the hole to deal with. Share this post Link to post Share on other sites
TT-(Moderator) 1,128 #8 Posted June 19, 2010 Use the chisel to break the thin half off of the gear. If it's still to close to slide it out past the crank, give it another hit. Sometimes I get lucky and they split in half and fall right off. Leave both shafts in the block so you don't have to bother with the holes. Share this post Link to post Share on other sites
PPGman 5 #9 Posted June 20, 2010 Well, i'll go with splitting the gear then. Thanks much for your help. Share this post Link to post Share on other sites
nichocli 0 #10 Posted June 21, 2010 Check the end play on the camshaft make sure it is in spec. It will make a terrible knocking noise if it is worn. Share this post Link to post Share on other sites
