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Modifying connecting rod?

1459 Views 6 Replies 4 Participants Last post by  woodpecker41
With over 1300 hours on her I know a possible repower/rebuild is inevitable.

What are some options for a direct bolt in replacement aside from the kawi that's already in it.

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SEW or Small Engine Warehouse sold a bolt in kit using an air cooled Briggs V twin. Not sure if they still do but it was plug and play and more rated HP. Roger
The rebuilt K301 engine in a 212 I purchased some two years prior from a WFM listing is so badly worn that the crank required turning .020 under. The Kohler rod is not offered. The machine shop said it is not a problem to bore the rod and machine fit a steel backed bearing. So we did.

Anyone know about this? From what I read on this site, folks wish they could do that. Is this rare? Is there a reason I find Iit isn't common? What to do with the pin end? If it is worn out then I will have a ton of machine work in saving the rod. I can buy an aftermarket rod with .020 oversize for dirt cheap on ebay .....
Scott, a lot of "puller" engines are done this way. I would recommend starting with a new rod when adding an insert. An experienced machine shop will make sure the crankpin bore is aligned with the piston pin bore.
The only one we have like that gets run with a governor and only spends minutes on the track compared to hours of mowing. But I've watched a lot of these same engines run way higher RPM (nearly double) without letting loose. Special built, special parts, but same insert in rod.
My thinking is a properly inserted rod is as good as a stock one, and probably better. I don't know if it is wise to go more than .020 under on the Kohler crank. Kohler stopped at minus .010 for a reason, probably liability issues.

Cleveite makes a bearing that works in .020. I used to have a picture and number of them and will see if I can still find it. Kohler cranks were surface hardened. Kohler says once you cut them more than .010 your are through the hardened part and that is why Kohler doesn't make .020 rods. Roger
Right. Thanks.

I figure that the pullers do something like this. I guess my question stems from a previous engine I had to build. The rod insert is impossible for some reason on the larger K series engines.

I'm not concerned about this working. Only that I can buy new .020 aftermarket rod for cheap and I will have a load of machine work in this old rod.

Another oddity to throw in is the reading on this site that the crank shaft does not wear because the rod is soft aluminum.
1. why does Kohler make oversize rods?????
2. why is my crankshaft rod journal worn-out??????

I can only speculate it stems from "I once knew this guy who....."
Crankshafts wear. I have seen cranks with gouges and when you use a micrometer they are way out of round. They are only hard for the first .010 inches which is 1/2 the thickness of a piece of paper. People don't change oil and run engines without oil caps and air filters on them. They allow dirt to enter the engine when pouring oil in or by not cleaning the filling area or funnel when using it. I know you don't do this Scott but the people on this forum are not average users. When I worked at a JD place we had a landscaper who leased equipment on a yearly basis and never even checked the oil much less maintained it by doing oil changes. Any of the K series engines can have an insert done. Some other Kohlers may not. The insert is not made for use in a Kohler engine. It is one made for an Allis Chalmers model G tractor. The ID is right for a Kohler crank and the rod is machined to fit the bearing. Go to Brain Miller's web site and he goes into detail on how this is done. The insert numbers are Clevite CB 278 and 279 or Federal Mongul FP59885CP and FP59885CPA. The rods are machined differently depending on the bearing use. The tabs are in different places. Roger
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