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LFinne

Kohler K301S rebuild question

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LFinne
In the Kohler manuals, the K301, 321 and 341 seem to use the same block. The difference in horsepower (12, 14 and 16) seems to come from larger piston displacement. The 301 and the 321 use the same cylinder head, while the 341 head has one extra bolt. I have two questions: 1. When I rebuild the K301, can I simply bore out the block larger and buy larger pistons, to increase horsepower? 2. Do the blocks come pre-drilled to take both cylinder head types(12/14 and 16)? I need to do a rebuild (starting to burn oil) and would like a little more power because of the attachments I run. Thanks, Larry

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HubbardRA
#1. You probably cannot bore to the next larger piston. The bores are 3.25, 3.5, and 3.75 respectively. .25 or 1/4 inch is more than the walls can take. When the pullers build the Pro Stock engines from the K341s the usually bore them about .180, and even then about 25% of the engines will blow out a cylinder wall. I would go with a stock oversize piston of .030 over to avoid ruining the engine. #2. No, the blocks are not bored for both patterns. 10, 12, and 14 used the same bolt pattern on the head even though the combustion chamber was smaller with the smaller bores. I currently have a 10 Hp head on a 14 Hp. You can gain a little power by raising compression. Watch out, higher compression means more heat. You don't want to cook your engine just to get more power. 16 Hp has a totally different bolt pattern on the head.

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LFinne
Rod, Thanks. I guess this means that the 10, 12, and 14 hp engines use different blocks, right (although the footprint and head bolt patterns are the same)? I thought they were the same blocks, just bored out differently. Larry

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HubbardRA
Larry, Usually, for cooling purposes, they do not want excessively thick cylinder walls. The thicker the walls, the more thermal mass you will have in the steel and the slower the heat transfer will be. This makes the inner walls get hotter with the same cooling fins and airflow over them. This is why they use the same basic block design, but the wall thickness in the cylinder is sized for cooling of the appropriate cylinder bore. Extreme overboring can be done for high performance tractor pull engines that fire up and run wide open the length of a 200 foot track. These engines will not hold up when used for mowing or plowing snow with an operation time measured in hours instead of a minute or two. I have been involved with garden tractor pulling off and on for twenty years. I have also done some drag racing, and was crew chief for a circle track car. The theory behind all engines is the same whether water cooled or air cooled. Material conditions must be kept within the designed working temperatures or else they deteriorate very quickly.

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10HorseMan
When we built a pulling engine, ''water cooled'' it ran 20 degrees hotter after the rebuild. We replaced the old sleeves with a 0.060'' larger sleeve. Also we upped the compression because the old one was a low compression engine and it would die out if it was not turning hard enough, but now it is good to the last pop.

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B.Ikard
I am in the process of repowering my 7012 into a 7014. The 12 hp K301 was blowing more smoke out of the breather than the exhaust. I looked at the situation from every angle and decided to get a used 14hp block, carburator and crankshaft and create a "7014". Seems to be the most bang for the buck. Ike

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LFinne
Thank you both for your replies. I've never pulled one of these motors apart, so I'm at a disadvantage. I bought a spare 12 hp engine to put in tractor while I rebuild the original one. Time is on my side. I'm waiting until next summer. I have a window of a few weeks, when the grass slows down but before the leaves fall (a couple of dozen oaks). I can't do anything now because I use the tractor to plow snow. It's using a little oil, but not that much. Beats shoveling.

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10HorseMan
Yep it was, Sorry if I confused anyone. My freshly rebuilt briggs runs warmer, so i dont let it idle for a long period of time because the higher the rpm the more air passing through the fins which cools it better.

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Mack
Larry, Rebuild kits that are available for Kohlers are-.003,.010,.020 and .030 oversized piston with undersized rods also available.As long as you have a good machine shop do their job on the block you should be able to rebuild yourself in the $200-300 range.A dealer should be in the $450.00-550.00 range.So,Depending on your abilities and the condition of the block you can save some money doing it yourself or you can have the piece of mind knowing that a good dealer will stand by his work.

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dhardin
Larry it sounds like you have a compression ring giving out. Allowing you to loose some comperssion into the crankcase, witch also means less power. Pull the head and see how much cylinder wear there is and bore if worn. If not just slap a set of rings in it and you may find a sufficient amount of regained power for your attachment.

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