K321 knocking

[Kaden]

I have rebuilt this kohler K321 and had it apart a handful of times there was a .010 piston in it so I ordered a kit to rebuild it using that size already bored out and when I start it there was a awful knocking sound so I tore it down and put a new rod in it I checked the clearance and it all checked out so when I got it all back together it still had this knocking sound as soon as I started it on a fresh rod I have read that they’re is balance gears in these that will make a knock sound and I’m just at a loss with this thing at this point I’ve rebuilt multiple engines before and never had this type of problem any help is appreciated

 

[T.R.K.]

Some kohlers had balance gears and some did not. If your engine had them, you should have seen them in there when you had it apart. You did put them back in according to the timing procedure in the manual, didn't you?
If you have balance gears they will make a knocking sound too if their bearings are worn. At one time you could still get the bearings for them but they run on the dowels in the block and I don't think the dowels are replaceable.
Did you measure the crank pin-where the connecting rod goes with a micrometer? Did you confirm the bearing clearance between your connecting rod and the crankshaft with plastigauge? In my experience if the bearing clearance is much over .0015 you will hear a knock.
also, did you re-use the ball bearings? (This may not be an issue unless they were really rusty or very badly worn.)
Another thing that will knock is if the piston is too loose in the block. It rocks back and forth as the piston goes up and down.

 

[Gene Davis(Ga.)]

If you use a std bore head gasket with an oversized piston, the piston hitting the edge of the gasket that hangs over into the cylinder will make a knocking sound. I learned this the hard way once.

 

[wore out]

Some kohlers had balance gears and some did not. If your engine had them, you should have seen them in there when you had it apart. You did put them back in according to the timing procedure in the manual, didn't you?
If you have balance gears they will make a knocking sound too if their bearings are worn. At one time you could still get the bearings for them but they run on the dowels in the block and I don't think the dowels are replaceable.
Did you measure the crank pin-where the connecting rod goes with a micrometer? Did you confirm the bearing clearance between your connecting rod and the crankshaft with plastigauge? In my experience if the bearing clearance is much over .0015 you will hear a knock.
also, did you re-use the ball bearings? (This may not be an issue unless they were really rusty or very badly worn.)
Another thing that will knock is if the piston is too loose in the block. It rocks back and forth as the piston goes up and down.

The "dowels" press into the block and can be replaced IF new ones can be found. The needle bearings in the balance gears are a bearing industry standard part, but there was a change by serial number, the O.D. of the bearings changed slightly.

The balance gears need to be shimmed to an endplay "spec" as does the camshaft, which will cause a knock if endplay is excessive.

Did you set the timing to "spec" using a timing light and varying the breaker point gap as needed?

All that being said, these are not the quietest engines ever made and will rattle on for years for no apparent reason.

I have a John Deere "214" that fits in that last category having rattled for longer than my grown children have been alive!

 

[Kaden]

Some kohlers had balance gears and some did not. If your engine had them, you should have seen them in there when you had it apart. You did put them back in according to the timing procedure in the manual, didn't you?
If you have balance gears they will make a knocking sound too if their bearings are worn. At one time you could still get the bearings for them but they run on the dowels in the block and I don't think the dowels are replaceable.
Did you measure the crank pin-where the connecting rod goes with a micrometer? Did you confirm the bearing clearance between your connecting rod and the crankshaft with plastigauge? In my experience if the bearing clearance is much over .0015 you will hear a knock.
also, did you re-use the ball bearings? (This may not be an issue unless they were really rusty or very badly worn.)
Another thing that will knock is if the piston is too loose in the block. It rocks back and forth as the piston goes up and down.

The crank clearance was .002 and kohler allows .0025 i wonder if whoever rebuilt it before had the crank turned but I wouldn’t think that clearance would cause this amount of knock there is also a lot of metal shavings being produced so a lot of me is thinking this is a piston slap I have also saw that these balance gears can cause shavings but prior to the rebuild it had no knock but was super low on compression and burned oil