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Dale

K301, 12HP Kohler Questions

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Dale
About ten years ago my dad gave me an old Allis Chalmers 912. He said he had just replaced the .030" overbored piston with a stock 14hp piston. I've used the tractor a lot and used it hard. Last week I broke a connecting rod. As I inquired about parts and machine work, 2 people told me not to overbore the cylinder, but to have the engine resleeved with a stock 12hp cylinder. They said the 14hp k321 engine used a different block. They couldn't refer me to anyone who could do the work. I still haven't found out if anyone nearby (Bloomington Indiana) will resleave the engine or what it would cost. However, due to to the relentless growth of grass, I'm also considering honing the cylinder and replacing the damaged piston, hoping I'll find a reliable solution to my powerplant woes before she blows again. So, I'm interested in getting reactions to this expediant plan. I also have junk tractors with Kohler engines in need of help. One tractor is a Wheelhorse with a 12hp Kohler. The other is a John Deere 110 (I'm not sure which Kohler engine this tractor has on it. I'm just wondering what problems, besides wear, might result from cannibalizing these engines for parts. I found a factory reference for engine bores: 3.8" for the 301: 3.5" for the 321. But I couldn't find a specification for the crank throw diameter, though one of the guys I talked to said you can only get a .010" under connecting rod. I'd also like to know what that crank throw diameter spec is, becase there are some marks on it. Thanks, Dale

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305SS
Dale I do not know if the wheelhorse has a wide block in it but if it does you may be able to put it in your allis. The fly wheel adaptor and a few other things need to be look at before making the swap. I say this because my 710-6 has an ariens GT-14 engine in it. I put it in myself, and it has been working great. But my stator wires come out on the wrong side,so for now I have the regulator bolted to the left hand side of the tractor. Some day when I get time I pull the engine and fly wheel and reroute the wires correctly. If Ray offers advice listen to him first.

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HubbardRA
The crankshaft throw is the same for a 12, 14, and 16. The 14 Hp piston is too heavy for use in a 12 Hp engine. The 12 Hp has a lighter piston and correspondingly a lighter counterbalance on the crankshaft. When you put a 14 Hp piston on a 12 Hp rod and crank, you are creating vibrations that will eventually destroy the engine. This most likely weakened the rod. A 14 Hp and a 16 Hp engine both have the same crank and the same weight pistons. A 12 Hp uses the lighter piston and has some of the counterbalance on the crank machined off to match the lighter piston. When the engine was bored to fit the piston, the cylinder wall was machined fairly thin, and most likely allowed the bore to deform into an egg shape and cause the piston to start sticking in the bore and break the rod. Hope this helps.

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HubbardRA
Bore for a 12 Hp is 3.25, 14 Hp is 3.5, and 16 Hp is 3.75. There were a few built that were called 14 Hp but had a bore of 3.625. Those were very sought after for tractor pulling in the 14 Hp class, since they were larger than the standard size. They all had a stroke of 3.25.

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Dale
Thanks for all the replies and I welcome more information. Does anyone know what the crank throw diameter is supposed to be for the 12hp 301. The 12hp Bore I stated in the o.p.(3.8")was a typo. The Kohler reference for the 301 I meant to site said 3.38", not 3.8" Has anyone had one of these sleeved? Dale

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Al
HI, Just checked the crankshaft book today, and the K302 and k341 use the same crank part numbers iin a number of specs. It is my understanding that the only difference is the bore and piston diameter. I know of many people that just bore the 030 k301s out to k321s and put the standard piston in it. I have done it and have had no problems. This what I would do instead of a sleeve. It is a heck of a lot cheaper. Matter of fact I talked to one of my Kohler friends, before I did it and he didn't think it was an issue. Officially he can't condone any modification beyond standard Kohler parts, and I respect that. We do not use aftermarket parts on anything we are franchised for: Briggs, Kohler, Tecumseh, Kawasaki, Robin, and Kubota engines. Simplicity, Gravely, Toro, Lawn Boy, Stihl. We also get parts for most brands on the market and usually use OEM parts there also especially belts. If I had all the money I have lost on aftermarket belts before I learned, I would be rich. Good luck, Al Eden

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Dale
Al, Well, it was bored out for the 321 piston about 10 years before I broke the rod. Did any of the people you knew to have put the 321 piston into a bored out 301 block use oversize 321 pistons in subsequent overhauls? As I said in the original post I am considering merely honing the cylinder and replacing the damaged 321 piston to avoid further structural degradation of the 12hp cylinder, because a number of people have cited pitfalls of the original overbore. I'd prefer a newly machined cylinder. I did talk to a local elderly man who had operated a used garden tractor business out of his home. He said he had a friend (now deceased) that did a number of these 301 -321 overbores and hadn't heard about problems that had been caused by it. His friend also did something (though he never knew what) to the engine head when he overbored the engines. Does anyone have a guess about what might have been done to the head. When my machinist looked at my stuff, he pointed out an indentation in the mating surface of the head and said the indentation needed to to be taken out. Dale

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Al
Hi, I wouldn't worry about boring it 010 or 020 on a 321 piston. When I first did this, I checked and the 301 and 321 share the same P/N head in a number of specs. Could you post a pic of the head? I know a number of pulling engines are bored to 4" and are really stressed putting out 60+ hp on alcohol. They strap the heads to the crankcase to stop the engine from failing at the base of the cylinder. A stock 321 should be a non issue. Al Eden

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Dale
Al, I'm too inept to send pictures, but the head is stock with a small impression of the gasket on the mating surface. I was considering taking the impression out by covering the bottom of the head with emory cloth and rubbiing over it a sheet of glass. I think I will try to reuse the cylinder, because some people say you can and I do have the 10 years experience of extreme service with the 14hp overbore. This would be my fastest alternative. I appreciate this is non-stardard and that I'm probably pushing it some. Afterward, I'll concentrate on putting together a (witihin specs) substitute. Could someone tell me what the diameter should be for the crankshaft throw? Dale

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