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Discussion Starter #1
Well as you all, I'm sure by now have seen, know I have to tear down my Kohler K321. Any pointers, tips, tricks, or any thoughts? I have helped tear down an engine once before, so I have an idea as to what I'm getting into.

I want to do this right the first time, but also I can't afford to replace everything. I know I'm looking at replacing rings, gaskets, and the crank rod. Am I missing anything? Right now I am not planning on surfacing the block and head, or over boring the cylinder.
 

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You really don't know what will need to be replaced in a tired/broken engine until you tear into it. Replacing "rings only" if the cylinder is out of spec tolerance is a band-aid fix that sometimes can lead to more headaches than if you left them alone. Bottom line for the cylinder/piston/rings is that IF the cylinder is out of tolerance, the only real fix is to get the cylinder right, and then fit the other parts to match.

The thing with your situation is, worn cylinder and/or rings probably doesn't have anything to do with backfiring. Unless I have missed something in your posts, this engine was "running" (requiring starting fluid to start) up until the time that you bought it.

Then, you weren't getting any spark, but now have spark and engine still won't start/run, but backfires while trying to start it, is that correct?

I don't recall in any of your previous posts whether a compression check was made or not, and what the results of that were, if any. If you haven't done it yet, do it, and possibly save yourself a bunch of grief. If you have good compression (or reasonably good) chances are, that you have eliminated the valves (and/or the timing of the valves) as being the offending internal component that is most likely to be causing the backfire.

In any case, the components that you have listed as the ones you are intending to replace (rings, gaskets, rod?!?) don't address the problem you are having with the backfiring.

<Insert standard disclaimer and the part about being my $.02 here>
 

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I agree with Longman except the compression test as these engines have ACR.. The most compression you will likely get is 60-70# barring any problems. The backfiring screams points or Carb trouble. The fact that you have to spray starting fluid makes a carb rebuild more evident. No spark is most likely dirty points or other problem..

**My disclaimer is $5 cents!
 

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Ok, I found this on one of you previous posts:

Well took the beast in to the shop to confirm my thoughts. The crank rod is broken. He removed the cylinder head and then spun the flywheel. The valves move and the points rod moves, but the piston does not move.

Guess I wasn't paying attention.

That being the case, I will just have to go with the first sentence of my previous post:

You really don't know what will need to be replaced in a tired/broken engine until you tear into it.
 

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I agree with Longman except the compression test as these engines have ACR.. The most compression you will likely get is 60-70# barring any problems. The backfiring screams points or Carb trouble. The fact that you have to spray starting fluid makes a carb rebuild more evident. No spark is most likely dirty points or other problem..

**My disclaimer is $5 cents!
Isnt there supposed to be some way to "temporarily" bypass or disable the ACR? Thought I read that somewhere.
 

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Discussion Starter #7
Ok to clear things up a bit. I had the head taken off. The valves still move up and down and the points rod still moves in and out. As of right now we are thinking that just the connecting rod is broke, as the piston does not travel up and down in the cylinder.

Right now I do not know if the crank shaft was bent when the connecting rod broke, or if it is still straight with in tolerances. I have no idea what the bottom of the block looks like. It might have been chewed up when the connecting rod broke.

Now that I’m thinking about this a little more maybe I should replace the crank bearings.? (just a thought) Are their any other parts inside of the engine that I should make sure to look at? I will double check parts when I take them out. Like stud bolts should they be replaced?

After I get the engine torn down then I will bring it into work and have the flatness of the head and the top of the block check, as well as the cylinder roundness. Many more correct tools at work to do this than I have.
 

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I like to take a lot of digital pictures before I tear something down that I'm not real familiar with. As you are going to have to buy a piston anyway, if the bore shows any wear, I would have it bored. Freshening up the valves while in the machine shop would be relatively inexpensive. To go to all the trouble of tearing the engine down and stopping short of doing it right isn't something that I would do. This is assuming that the rod didn't damage the block or crank on the way out. I don't have experience with the after market rebuild kits so I'll let others advise on that but I hear that they are very reasonable.
 

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Discussion Starter #9
Well update time....

As we thought the rod is dead, I counted 6 pieces that I could pull out of the oil pan. A lot of metal shavings still in the oil pan. The crank looks to be toasted also, as it is VERY badly gouged, dinged, ad beat up. It smells to me as the oil has been burnt a few times in this engine.

As I was pulling the engine out I found that 2 of the mounting holes to be stripped, one mounting bolt broke of in the block, and the last to be very tight (almost like it was cross threaded).

Here are a few pics.

Crank shaft


Pieces of the crank rod in the oil pan.


Top of the block.


Head
 

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Discussion Starter #10
I am actually kind of happy that this happened before I bought the tractor and that I got the tractor for a good price. Now I don't have to worry about this happening to me while I am using the tractor.
 

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That crank may clean up OK. The rod does not look like it was overheated as it would from lack of oil. Judging by the small stub left on the piston, the engine was over-revved. Carbon deposits look good, doesn't look like it was using oil. Clean up the crank, new rod, new rings (and piston if you want), and put it back together.
 

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Discussion Starter #12
Lastest update on the K321. I have now taken it to two shops that have very good reputations. Both said that with the crank being gouged soo bad that it will have to be replaced as well as the piston and connecting rod. With the other small problems with this block, as of right now, it is not a good candidate for a major repair/overhaul.

I am looking into getting a reman. K321 to drop into the Case and get this tractor up and running. When time and funds become available I'll dig back into this engine.


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