Re'ringing a kolher engine

[BigBill]

I been thinkin since my 108 and my 100 need rings why not just ream the ridges and hone the cylinders and put in new std rings since they can handle up to .009" oversize. Of course if the cylinders aren't scored or way too oversize. I don't hear any piston slap on either engine too. Both bores are standard size.

But my 108 seems to only have some blowby when its hot. Plus the exhaust is really loud that gives me a thought that the exhaust valve needs to be adjusted because there may not be any clearance in it thus loud and running hot just maybe a clue. It just runs too godd to have anything seriously wrong with it. I have blowby but no smoke in the exhaust. Weird? I need to pull the engine apart soon i just order some gaskets/parts for it.

This makes me ask another question how often do you check your valve adjustment on your cadet? Since most of these engines are the orginals maybe its just a valve adjustment in some cases, maybe?

I fixed a kolher on a gravely once with just a new set of rings. The bore was a little past 030" over and it was perfect. It ran great just with new rings. Lets face it .002" is the thickness of a hair on your head thats not much to be oversize or past the tolerances.

Maybe I been too fussy in the past ready to bore oversize all the time when i didn't have too.

Now remember the ridge at the top of the cylinder needs to be completely gone before new rings can be installed. Or the new top ring with the square edge will break the ring when it hit the rounded worn edge of the ridge at TDC. Don't let this get you into trouble so ream that ridge.

[Eugene]

Checking the valve tappet clearance. Every so often in my case. Usually when I do a full tune up. Really depends on the engines usage. I have one Cadet that only get used as a snow blower and only started and driven to keep things working when not blowing snow. I haven't checked the tappet clearance on that one in 3 years.

[George Willer]

Bill,

I try really hard not to spend money on unnecessary engine repairs but IMHO an engine with .009 cylinder wear is way past redemption.

I don't know about cadets but real Cubs have an allowable ring gap of .007" to .017". Considering a starting point of .007" gap, the worn cylinder diameter of +.009" times pi would tell you the ring gap before any additional wear is considered would be .035". That sounds WAY excessive. Consider that the recommended .007" is a cold measurement and is expected to aproach .000" at operating temperature.

Why invest the price of a set of rings on an engine that is beyond worn out?

[BigBill]

I'm saying with a cylinder thats within specs on the ring gap but out a few .001's like my .030" gravely kolher engine was. The bore was .032" and i got by with .030" rings and it ran fine and went back to work.

They say that standard rings are good up to .009" so if we fit them in a cylinder thats .002" over it will work and be ok. Redoing a .009" bore is out of the question its too far out. With an air cooled engine there is a heat transfer from the piston to cylinder too thats part of the engines cooling so we can't go too big on the clearances.

I ran one of my drage race engines in one of my suburbans and it has .007" piston clearance. The norm for cast pistons is .001" to .002" and forged pistons is .005". I put in .030" rings and let it go just to test it. The engine lasted for well a 100,000 miles. It was used for a shuttle from Ct to Vt. My quickest run door to door was 2 hours 25 minutes. Thats from waterbury,Ct to central Vt. While it wasn't a big block it sure held its own for a small block.

This is why i'm starting to think we have more tolerances we can deal with in bore clearances. While there is a difference between air cooled engines and water cooled engines too.

I'm going to test a 10hp kolher soon and write all the specs down and track the engines performance and life. I have a std bore that needs rings. If its not too oversized already I'll ream the ridge, hone the cylinder and mic the bore and put in std rings and fit the ring gaps. I'd like to see if it has a shortened life or the same life as a bored cylinder with a new piston.


I just ordered a new ridge reamer, a set of hones and a bench valve grinder and I'm looking at a new boring setup so I can do my own boring again. I don't like to have anyone do my work. I had trouble in the past. I need to set up my shop again.

[Paul B]

I don't know if the standard rings are good up to .009 over are not, but Kohler made pistons in standard, .003, .010, .020, and .030 sizes, and the standard and .003 used the same rings.

When you measure the bore on a Kohler, do so at several places from top to bottom, and at 90 degrees around the bore from each measurement. The bore will usually wear more at the bottom than most engines, the top can be in tollerance and the bottom be out by several thousands.

[BigBill]

The ridge at the top of the cylinder is actually wear. I have seen on engines run with low oil levels have two ridges one at the top and one at the bottom only were the rings travel.

My uncle god rest his soul was never one for checking the oil levels in anything he would drive his car till the oil light came on. I changed 3 engines in the same car for him. The first two were cheap because i did the machine shop work but the last one we had a machine shop do it( i didn't have the time) and it cost him so he learned to check the oil from then on. Other than that he was a hell of a guy. Sometimes i thought he thought the oil light was an electric dip stick. He was an old farm boy from VT.

I've done a lot of machine shop work too. I just think if the bore is close enough and not too oversize we can sneak in a std set of rings with a hone and reamed ridge and get by with that. Saving the cylinder for boring down the road. Sooner or later the kolhers will be harder to find.