K301 to K321 - boring...

[Tuneup 1,433]

Howdy Gurus!

 

Well, it took several months but I have the old 1980 C125, rescued from a Southern backyard, cutting grass so it's time to start disassembly for restoration. What a road it's been! The stereotypical redneck treatment (read creative) was applied everywhere...

 

Anyway, first step was to move the tired 12HP Kohler yesterday. She smokes on load so I'm sure it's had a hard life and some abuse. Bore looks fine when the piston is up top (std piston) but I can see plenty of ring when she's in any other position - I don't have a bore gauge but the compression ring gap is well over the .030 limit. Crank journal clean.

 

So.......given the fact that this engine is in otherwise good condition on my bench in pieces, can I just bore to the 3.5 spec and put a 14HP piston kit in there? Seems plenty of metal to allow 1/16 removal on each side. I've seen on the Internet (which is never wrong) that some have done it before me but know nothing of the longevity. Perhaps Kohler uses the same block for the 10-14? If too risky, it will simply be an .030 clean up.

 

Inquiring minds want to know. While you ponder your response, I'm off to stand in a government line on my day off to renew my driving license...

[Tuneup 1,433]

Let me clarify on that redneck statement. I had to correct for it everywhere. Former owner quite creative. It read like 'I' applied it - not!

[Ed Kennell 37,998]

Hey Tuneup....not a Guru on rebuilds, But I really feel the  K301s were the best Kohler made.  Unless you really need more HP for tilling or snow blowing, I would stay with the 0.030" oversize 12 HP piston.  You will be increasing the bore nearly 1% and gain some HP.      

 

BTW, enjoy your day renewing your drivers license.  Pack a lunch and newspaper.

Edited December 29, 2015 by ekennell

[oldredrider 2,548]

Personally,  I would stick with the 12hp piston. The 14 piston weighs more and could cause a balance problem, especially noticeable on a cradle mount motor. That is, unless you plan on having the motor balanced by an engine shop.... $

[prondzy 3,881]

If you read online, a guy can probably make it fit a 14 in a 12 BUT......... Longevity will suffer. The block walls will be too thin for heat load and you could end up boring through the sidewall....oops there goes the block. I would clean up the cylinder to the next biggest bore allowing cleanup of any scoring while still allowing for future rebuilds. If it is STD. Bore, clean up to .010 or .020 .  I would not bore out to .030 right away this is not a small block chevy it's a kohler, you will feel no power gain between std and .030" and if you need more power than a 12hp  buy a bigger motor or get a bigger tractor. The k301 is a power plant, give it a rebuild you will be impressed with the results. A clean work area, a good machine shop, and proper break in are the keys to a strong lasting rebuild.if you have any questions feel free to PM me.

[Tuneup 1,433]

Thanks guys,

 

Yeah, DDS in west Georgia is just fine (unlike the NJ hell where I grew up) so one can have fun waiting, even if I was 342 and they were on 299 when I got there.

 

I expect this engine will be much different after the rebuild (runs well but not very strong) and, yes, I don't want to jeopadize its reliability. Love those Kohlers! Now to locate someone in the Atlanta area that can bore and hone for me.

[Wheel-N-It 2,968]

5 hours ago, ekennell said:

Hey Tuneup....not a Guru on rebuilds, But I really feel the  K301s were the best Kohler made.  Unless you really need more HP for tilling or snow blowing, I would stay with the 0.030" oversize 12 HP piston.  You will be increasing the bore nearly 1% and gain some HP.      

 

BTW, enjoy your day renewing your drivers license.  Pack a lunch and newspaper.

Tuneup, rebuild the 12hp as a 12hp, don't try to make it a 14hp. With a fresh rebuild you will have plenty enough power to operate a 48" mowing deck, run a tiller, and push or pull anything that needs pushing and pulling providing you get enough traction. If your carb throttle shaft has any play in it at all, have the carb gone through or buy a new one. The one knock off carb I have on a 14hp Kohler works just fine. The shaker plate K301's are a good old work horse engine in the C-125. I just gave a 1984 C-125 to a friend, and even though the old K motor smokes and uses oil, he loves it   This is a guy who knows Cummings diesels like the back of his hand so go figure LOL LOL

[Wishin4a416 2,191]

I think .125" is way to much to take out of that bore. In fact I would only take what you need to clean it up.  .010 if that does it. No need to go oversize unless needed. That way it can be done again down the road if needed. I have read where the pullers have taken .250 out of the 13 fin 341's and run a 4" Chevy piston but that block has a lot of meat on it. I just did a 321 and just took .010 because that cleaned it up. Good Luck!!!

[Tuneup 1,433]

Sounds about right. The 12 stays a 12. Thanks, all! I've got a friend with the tools so will measure just how 'out' this bore is. Well worn but never bored before so salvageable. Looking forward to everything this machine needs. It's been plenty of fun so far. So much TLC needed.

[Ed Kennell 37,998]

Might be a good idea to determine how much overbore you need to cleanup.  Then buy the piston and final bore to match the new piston.

[953 nut 55,021]

9 hours ago, Tuneup said:

I'm off to stand in a government line on my day off to renew my driving license...

 

Last time I renewed mine in North Carolina I did it on the internet, now that I am officially an "Old Fart" I will have to go in for an eye test next time.    

 

Glad you decided to stick with conventional rebuilding.   

[Shynon 7,459]

7 hours ago, oldredrider said:

Personally,  I would stick with the 12hp piston. The 14 piston weighs more and could cause a balance problem, especially noticeable on a cradle mount motor. That is, unless you plan on having the motor balanced by an engine shop.... $

The crankshaft on a 12hp is the same stroke as a 14 and 16 but it is lighter weight. 14 and 16 are heavier to balance the extra weight of the piston.

[Tuneup 1,433]

Georgia is upping the anti on licenses so they can reliably be used as ID for voting. It takes a visit if you have one of the 'old' ones. Good to know I have a lightened crankshaft. Yeah, will stay with conventional approach. I have a friend who ran one of those old car parts houses before the franchisers got in. Remember those places? Cylinder boring - no problem. His shed out back is a treasure trove of 'stuff'. We should be able to get that 301 bored and honed nicely. Thanks, all!

[WHX?? 48,749]

Idea might to put one or more of the old rings back in the bore and measure the ring end gap. That might give you an idea of how big OS you need. Get that new piston & rings and when you find that machine shop with the good guys and fair prices (yah right good luck with that)  they could fit the fit the bore to the new os piston/rings.

[Tuneup 1,433]

She gaps at .041 consistently down the bore so time for a mild bore job. I haven't ringed-up old Jimmy up the road in a while. He's a good 'ole boy and has the tools to do just about anything to an engine. Should adapt to a Kohler, I'm thinking.

[Shynon 7,459]

He should have a bore gauge, take the block with and have him measure, He will be able to tell you what piston you will need.