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FrankieC

K321 REBUILD

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FrankieC
If this belongs in Shop Talk, or somewhere else, I'm sure it'll get moved. :) Last winter I got a K321 with a nice big hole in the side of it where the balance gears let go. It's the style that has a bigger intake than exhaust valve. This fall I got a replacement block -- both valves the same size. I'd thought I'd just interchange what parts I could. Yeah, right! The "new" block is standard bore and last night I found the old block is .030 over. No big deal, really, because I plan to have the new block rebored. Also, I don't plan to replace the balance gears. 2 questions at this time: Should I plan to have the block rebored to the max of .030 or just taken to the minimum? Should I remove the balance gear shafts or leave them in place? I'm in no big hurry -- winter doesn't officially start for 4 more days!

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Wishin2BMowin
If it's a brand new block why would you want to have it bored out at all? If you do this you are lowering the compression ratio and it would most likely cost you more than if you just bought a standard size piston and rings. If the block is used is the cylinder worn or have scratches? If not just use a cylinder hone to rough it up so the rings seat and buy a new piston & rings. Good Luck...

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HubbardRA
First of all, I do not understand why you would want to bore a new block. I'd put in a standard size piston and have basically a new engine. This will leave room for re-bore several years from now, if needed. .030 oversize on the bore will be such a small power increase that it will not even be noticed. Secondly, the balalce gears do not affect the operation of the engine. The engine doesn't care whether the gears are there or not. What the gears really do is eliminate some of the vibrations from engine operation that will be transmitted through the chassis to the driver. You will probably notice a difference in tractor vibrations without the balance gears. From my experience, Kohler engines create more vibration than B/S engines, even with the gears installed. One more thing. If the entire crankcase is not shattered, you may be able to weld up the hole in the original engine and rebuild it, without the gears. Just a thought. Wishin2Bmowin, Boring an engine "raises" the compression ratio, since you are squeezing a larger volume into the same size combustion chamber. The formula is (cylinder volume + head volume)divided by head volume. Since the cylinder volume will be larger, the compression ration will be higher. When the factory increases the bore on an engine, they will usually increase the volume in the head to keep the compression ratio where they want it. Easiest way to raise the compression of a 14 Kohler is to bolt on a 10 Hp head, which has a smaller volume than the 14 Hp head, but uses the same bolt pattern.

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Wishin2BMowin
HubbardRA, Thanks for the lession on the compression ratio. I thought it was the other way around. I once rebuilt a 77 Datsun 6 cylinder to .040 oversize and was able to run it on regular gas so I thought the compression was less after it was bored out? Guess I was wrong again? Have a happy holidays...

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FrankieC
The "new" block is actually a used block from Joe's Outdoor Power in Michigan -- got it off eBay. The old block has a hole in the side of it you could put your fist in! Last night I finished stripping them both down and have an idea that the governor on the blown engine let it overrev. It's evident that it had been rebuilt in the past. With no measuring tools, I think the best way to know where I stand with the bore and crank journal is to have them machined before I buy a rebuild kit. An engine stand is a big help. I'm realizing that this isn't rocket science and started this thread in the hopes of possibly helping someone else get over the "fear factor" of rebuilding a Kohler. :)

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FrankieC
:) He's baaack. Learned a little. Learned questions can be good, so.... how important is the .003" "play" on the crankshaft? Oh, and how do you measure the compression on an engine that has a built in compression relief? Nothing compared to what Steve McQueen's going through right now on "The Sand Pebbles". :D

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BLT
I think .003 is OK and as far as a compression check with relief pin, in don't happen. You then have to check things with a running engine. You have to go thru the Kohler book to confirm. You should be able to download the book at no charge.

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B.Ikard
quote:
Originally posted by FrankieC Oh, and how do you measure the compression on an engine that has a built in compression relief?
I think Kohler recommends a U tube manometer. It is a simple tool used to measure crankcase vaccum. These are little used but very informative. Basically an engine with a worn cylinder/low compression will pass excessive blowby to the crankcase creating a pressure instead of the normal vaccum one would find in a good engine. Of course a badly leaking seal/gasket will throw the numbers off. Ike

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