Grasshopper zero turn Kohler twin cylinder CH25S engine rebuild, pistons, rings, other stuff PART2

[@noahwilson6162]

I’ve been looking for a rebuild video of a kohler twin like this forever! I’m so glad I found this video. Thank you!

[@whatsnextgarage]

If you run into any issues just send a comment. I’m usually pretty quick to respond! Have a great holiday season!

[@rossxxxx]

Perhaps I'm wrong but I always thought you had to measure cyinder wear further down the bore. The lip of the cylinder isn't even in contact with the rings and will stay at manufactured size even tho the bore maybe worn and ovalled to buggery. Thanks for the clip. I'm just about to start doing the rings on my 730. Compressions at 108 instead of 160. I was thinking of doing a leak back test but decided to do rings and get valves lapped at the same time. Then keep it as a spare while I put on a Chinese 33hp. Half the price of comparable Kohlers or Vanguards. I'll be happy with three quarters of the life. Your clip is simple and easy to follow. Thanks

[@whatsnextgarage]

Thank you very much! Yes you are correct about cylinder wear. Good luck on your project, it sounds like you have a good plan in place to get your machine back on its feet!! Have a great weekend!

[@sidnum]

Great vid!

[@farmerrick9660]

Good Evening!, I have a Kohler Command ch18 I just pulled out of a small skid steer, it was leaking oil and wasn't charging, after pulling the cover I noticed the flywheel was loose, took the flywheel off to find a big mess, the crank has play in it, so much it destroyed my magnets and stater, obviously the oil is leaking from the seal. Im guessing before I go any farther is there a bushing in the block or is the block Junk??. Thanks for your time ..

[@whatsnextgarage]

Good evening to you as well, I vaguely remember no bushings. So I believe you’ll either have to do some fancy machining or scrap the block.

[@farmerrick9660]

@@whatsnextgarage thanks for the quick reply, watching a few rebuilds now, dont see anyone changing a bushing, just a seal, unless theres a sleeve on the crank, hard to tell from pics?

[@whatsnextgarage]

@@farmerrick9660 no bushing on the flywheel cover. It just runs in that aluminum bore that’s counterbored for the seal.

[@farmerrick9660]

@@whatsnextgarage Thanks, that's to bad, engine has great compression , I don't understand how this happened, plugged oil hole?

[@whatsnextgarage]

@@farmerrick9660 very well could be or at sometime in it life it was run low on oil. That’s gotta be a neat little skidsteer though.

[@stephenbay9564]

Great video...need help with a question here. When you we installing the pistons, on each one you said: "Make sure we are pointed to the flywheel". May I ask - what - was pointed towards the flywheel? What on the piston were you looking at, to have IT pointed towards the flywheel?

[@whatsnextgarage]

@@stephenbay9564 I believe there is a recessed dot on top of the piston. If you’re pulling the heads off you’ll see right away.

[@stephenbay9564]

@@whatsnextgarage Wow....Thanks for a fast reply! And thank you for that answer. I will check the pistons. And until you said about facing the flywheel I was thinking that the orientation had more to do with the asymmetrical connecting rod ends that this engine has, where one end is a tad longer than the other, and it was meant to clamp to the crankshaft in one specific direction (only). Now not asking you for the answer here, but what difference does it make to the piston, which side of it faces the flywheel? It can only go in ONE of TWO ways, and one way the connecting rods will not hit the crankshaft as they should, no? Gee such a simple thing and yet it's not blatantly simple it seems.

[@whatsnextgarage]

I can honestly say that I have thought that same thing. I finally came to the conclusion that the mark on the piston simply makes sure that when you reassemble a used motor using the original pistons they go back in the way they were worn. Now I’m curious and I will be diving into it.

[@stephenbay9564]

@@whatsnextgarage This is what I found: "Asymmetrical connecting rods, also known as offset connecting rods, have a big end that's slightly offset from the rod beam's centerline. This design is intended to accommodate engine designs where the cylinder bore's centerline is also offset from the rod-bearing radial centerline." And so from that....if THAT is the case.....then installing the connecting rods in the correct orientation is fairly critical. Now on another KZbin video a guy showed the top of the piston and it has the word "fly" on in, with an arrow. So OK, I can go along with that. BUT it would seem to me, that when one installs the wrist pin to the connecting rods, that THEY TOO should go in one way. Because if not, that non-symmetry of their ends in going to wind up hitting the crank one way now, and another way on the next one, if the attachment of the two is not controlled. To be clear.....I don't have an issue with the pistons going in either way, because I don't see it mattering much. But I DO have a problem with the connecting rods not mating with the crankshaft as they were designed to do the mate.

[@whatsnextgarage]

@@stephenbay9564 thanks for that detailed description!! Have a great weekend!!

[@davidmccauley906]

What determines the Head number. What side is Head 1?

[@whatsnextgarage]

The number is cast into the heads. I’m not sure off hand which is which.

[@derpyrage3852]

What the reason to get the glazing off? What is the glazing for

[@whatsnextgarage]

After years of any motor running the cylinder bore starts to wear. The wear is normal and starts to smooth out the cylinder walls. That surface develops a “glazing” effect that, during a rebuild, should be honed out. Once the glazing is removed and a fresh cross hatch is established, the new surface can wear in with the new piston rings.

[@lenjames]

When installing new rings you must hone the cylinder wall. Why...because the glazing he mentioned is a coating of combustion material that coats the cylinder wall. When new rings are installed they need a honed (clean) wall so they wear in right. This sets the rings to do their job providing a sealed combustion chamber. Honing is done lightly to just remove the glaze. To aggressive and now your taking to much wall material away and may increase bore size. That's a bad thing. This is a simple explanations. Hope it answered your question.

[@whatsnextgarage]

@@lenjames simple?!! That is a spectacular explanation! Thanks a lot for your feedback!

[@paulthompson1654]

Kohlers get cam lobe/lifter wear , Rocker bolt fatigue , crank end float likes to be minimum spec After market automotive quality rings are far better than Kohler . Cross hatch for kohler is 33 degrees [control of oil but wears rings quickly] In a machine shop professional cross hatch at 45 deg is way way better than kohler ever did . ****Some early engines are Nika-sil bores ****** late 90`s kohler DID NOT use fire rings on the head gasket Inlet manifold /head sealing was very bad same as exhaust sealinghead . solution is to machine surfaces . Overheating occurs alot in the 25 hp with 52 inch or larger decks . These motors will go to 230f--250f oil temp in 90f or up weather . LARGE OIL COOLER IS NEEDED

[@whatsnextgarage]

Wow thanks for all that awesome information!!