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East Coast Lawn Choppers
10-10-2009, 04:43 PM
Has any of the rebuilders in here ever run into cylinders that can't be glaze busted or honed ??? We have three of them now... a 25, a 26 and a 27 they will not hone. It is almost like they are nickosil cylinders, but they take the same rings as all the others. The latest one is a 25hp CH25 spec 68606 and we ran the hone in it and it won't touch it at all. We bored one of them so we could use it. We still have 2 more here yet that I didn't want to bore. We even took one to the machine shop and asked him to try it , he put pressure on the stones and even went to his rough stones... barely left a mark in the bore. Only thought other than a crome bore is a lot of hours on it possibly overheating and causing it by heat treating the bore ???
Any thoughts or knowledge ?

Restrorob
10-10-2009, 06:17 PM
It is almost like they are nickosil cylinders


Bingo,

Right from the manual, And it applies to both CV and CH engines. When I run across one I shortblock as stated.....


http://i107.photobucket.com/albums/m314/Restrorob/Kohler/KohlerCylinderBoreInfo.jpg

East Coast Lawn Choppers
10-10-2009, 06:41 PM
So I guess that is what it is... and they don't sell... or atleast my dealer the special rings for that bore. Even the kohler site lists the same rings for that spec as for the std ones. We have a machine that shop said they can bore them. We bore some but most we send out. Well if I have to do the shortblock at least I already refaced the valves and ground the seats and the heads are ready. It would have been back together today but... damn nickosil
Where is the best place to get shortblocks at a good value ?
or do you know whats the part number is for the proper rings because the cylinders look like brand new.
Thanks

Breezmister
10-11-2009, 12:24 AM
Bingo,
Right from the manual, And it applies to both CV and CH engines. When I run across one I shortblock as stated.....


Interesting, and this does not apply to the CH 27 ?

And if I gave you the spec number off a CH 25, could you tell me if that is one of the chosen engines ?

Restrorob
10-11-2009, 09:38 AM
Interesting, and this does not apply to the CH 27 ?

And if I gave you the spec number off a CH 25, could you tell me if that is one of the chosen engines ?


No, From my knowledge only the 25's and 26's......


To find if your engine has the nickel bore, All you have to do is look up a piston or ring set. Kohler does not offer over-sized pistons/rings for the nickel bores only standard replacements for if the bore is still with-in usable specs, They only list over sizes for the bore-able cast iron cylinders.

Breezmister
10-11-2009, 10:14 AM
No, From my knowledge only the 25's and 26's...... They only list over sizes for the bore-able cast iron cylinders.

Thanks Restro, that explains alot :drinkup:

East Coast Lawn Choppers
10-14-2009, 11:17 PM
No, From my knowledge only the 25's and 26's......


To find if your engine has the nickel bore, All you have to do is look up a piston or ring set. Kohler does not offer over-sized pistons/rings for the nickel bores only standard replacements for if the bore is still with-in usable specs, They only list over sizes for the bore-able cast iron cylinders.

It is weird thou. All the dealers in our area and the Kohlerplus website say that they take the same rings as the std bore. From the spec # on ours it comes up with the 24-108-04-s rings (now 24-108-14-S) and they list over sizes and all. Did they start using just plain iron rings in all of them now ?
Do you have a part number for the 25-26 hp rings for the nickosil bore ?

Restrorob
10-15-2009, 07:17 AM
My Kohler dealer's website only shows standard rings for your CH25, The same number you posted. If the cylinder was bore-able they would have listed over-sized rings under the standard rings part number.....

East Coast Lawn Choppers
10-15-2009, 05:11 PM
So it does look like they almost all take the same number. The CH25 with the nikosil only lists std, but if you go to CH745-0007 it takes the same number std rings and then lists oversized too. I thought I remember a some of them having a chrome face top ring but now all the ones we get are all plain iron rings.
Thanks for the help resto

VegetiveSteam
10-16-2009, 11:02 AM
All CH,CV 25 engines and some CH,CV26 had the nickel silicone plating on the cylinders. Don't confuse that with the 25hp CH,CV730 which were cast iron bore. An easy way to know the difference is put a magnet to the bore. If the magnet attracts itself to the bore then it is a cast iron bore not nickel silicone. Also I know I'll get arguments on this but all Kohler rings are chrome. I know they are black and not shiny like you might think chrome would be but they are chrome.

East Coast Lawn Choppers
10-16-2009, 02:42 PM
All CH,CV 25 engines and some CH,CV26 had the nickel silicone plating on the cylinders. Don't confuse that with the 25hp CH,CV730 which were cast iron bore. An easy way to know the difference is put a magnet to the bore. If the magnet attracts itself to the bore then it is a cast iron bore not nickel silicone. Also I know I'll get arguments on this but all Kohler rings are chrome. I know they are black and not shiny like you might think chrome would be but they are chrome.

I'll have to research some of this better I guess. I know looking at the part number for those rings and when I go to the "where used" they use that same set of rings all the way up to the CH745 I know they are cast iron bore. So they use the same rings on nikosil bore and cast iron bore. Also the rings use to be shiney chrome faced. Do chrome rings work in a nickosil bore ?
I always thought from my dirtbike eperience they used different rings for nickosil bores. So if we tried boring that bore we would go to aluminum in a few thousands' of an inch.
Well we will see how this one turns out we threw it together and fired it this morning. It is on the break-in stand... oil pressure looks good, charging good, etc.... so far so good and no smoke yet now to go put a load on it.
Thanks guys... I haven't had too many of the older ones here so just started running into the nickosil... now that times are getting tough and these old ones are coming out of retirement.

VegetiveSteam
10-16-2009, 03:31 PM
Yes the CH745 cast iron bore and the CH25 nickosil bore are the same size bore and do use the same ring set. Kohler does use the same rings set on both bores. If you do try to bore the nickosil cylinder you will get into the aluminum in .001 or so if it will even cut through it. Is the bore in bad shape? If the bore isn't damaged you should be able to wash it out and just install new standard rings. If the bore is damaged I don't think I'd waste the time or money trying to bore it. Probably best to short block it at that point.

East Coast Lawn Choppers
10-21-2009, 10:07 PM
bore was good, just threw new rings in, just can't believe they would seat without honing, but they did. Runs great... now I have three more of these to rebuild that I sat aside for this reason. Couldn't believe that they actually made some of them with the nickosil. Over 100 engines rebuilt this year and only had three with nickosil, most of our 25's were the 730's
Thanks for the help everyone, as often as I read that manual I never caught that one small paragraph...

Restrorob
10-21-2009, 11:27 PM
as often as I read that manual I never caught that one small paragraph...


Sometimes it's the smaller things we over look....

Glad to hear it worked out !

tomo
10-22-2009, 04:56 AM
hi,
Kohler bores 25hp block with nicklesil bores
Ask any long time walker owner
From memory walker swapped over prior to the 730 series engines
The nickle bores were a disaster for walker
Explain

combine the poor aircleaner housing seal upgraded now
The 25hp develops more heat than the 20 hp ,bad for any nickle sil bore pits and delamination occurs
In the earlier years there were no cleanout covers on blower cover this caused high temps in engine

To hone a nickle bore is not recomended but u can buy specialist hones
They are a super fine grit
Most of this comes from the motor bike industry

There are 3 types of rings
1/ Chrome

Typically used on soft bores eg cast iron
Rings wear is slow but bore wear maybe a little faster
Ring material is harder so a very small amount of contaminated air is tolerated

2/ Moly coated rings
3/ cast type

2 and 3 engine runs in better as the rings are softer than chrome .The moly ring runs in even better than the std cast type

The other MAJOR concern is the hone angle of cross hatch
on the niksil / cast bores
KOHLER recommends 26--33 degrees VERY VERY WEIRD :hammerhead:
This is only done for better oil consumption control and quick bedding in of the hard rings
Recomend bore out nicklesil and fit cast liners at normal 45 degree cross hatch with a moly ring

## hone cylinder bores in a proper machine avoid hand type ,,reason as a kohler particulaly a 25 hp develops so much heat compared to 20hp, bore distortion and poor ring sealing needs to be perfect . AN air cooled engine distorts way more than liquid cooled also


Also kohler uses metric rings
Use rings from a japanese car from an OEM ring maker who has an aftermarket listing

The original pistons and rings are Mahle made anywhere all over the world

PS does any body Know where u can buy engine parts at a fair cost so u can actually rebulid cheaper than buying short motor eg crank rod piston kit

I have come across a dealer who put kits together but do not remember name ..
Most places price short motor cheaper than parts :hammerhead:

tomo:waving::waving: