Kohler engine ring gap problem

[ACmowerguy]

Hi.

I have a 16hp k341 Kohler I am rebuilding. It was freshly bored .020 over. I have a new .020 piston and rings, these are PrimeLine aftermarket parts. I have had them for quite a while (couple years) and am not sure I could send anything back. I checked the ring end gap on the top compression rings and found that the very top ring has 25 thousandths gap. The kohler manual states that it should be no more than 20 for a new ring, but that 30 is acceptable for a used ring. The lower compression ring is just fine at about 15 thousandths. Do I need to get a different ring or can I still use this.

Thank You.


-Chris

[Steevo]

It'll work, but . . . .
Was the cylinder bored for the piston you have?
If so, I would worry that the cylinder clearance is too large.
The rings came with the piston, both specified for .020" overbore.
If the piston/ring manufacturer is working to the Kohler specification of .015" for ring end-gap, then the cylinder bore diameter must be larger than desired. It is more common to have to file the ends of a ring to attain minimum gap than to have to worry about being too close to maximum.

[Tencubed]

I'm inclined to agree with Steevo. Think I'd take that block somewhere besides where it was bored and have the bore checked. Could be they cut it out oversize. Probably not but I'd sure check it.

Take the piston with you and see if the bore is proper for the piston, remote chance you have a ring that is just a tad loose.

Mike

[Pintony]

0.005???
A piece of paper is 0.007 .....
I do not see what the big deal is???

[eastonct124]

With heat and expansion....005" is a big deal.
On the race engines I used to build (BB chevies), we always ran .012" file fit.
Too tight, you'll score the cylinder from expansion, too big, you psh oil, and lose comp.
There's a reason for factory recommended gaps.

[Pintony]

Originally Posted by eastonct124

With heat and expansion....005" is a big deal.
On the race engines I used to build (BB chevies), we always ran .012" file fit.
Too tight, you'll score the cylinder from expansion, too big, you psh oil, and lose comp.
There's a reason for factory recommended gaps.

Is your race engine air cooled???
C'mon we are talking a tractor engine not a RACE engine.
It is not like it is .005 on the bearings...
THAT would be a BIG deal!!!!!

[eastonct124]

Originally Posted by Pintony

Is your race engine air cooled???
C'mon we are talking a tractor engine not a RACE engine.
It is not like it is .005 on the bearings...
THAT would be a BIG deal!!!!!

Exactly, aircooled means more dramatic changes in heat loss, and heat gain....also inconsistent heat pockets.

Everything in regards, whether it's a race engine, street engine, work engine... car, truck, or tractor....ring gap has a dramatic effect on performance, and endurance.

[Pintony]

Originally Posted by eastonct124

Exactly, aircooled means more dramatic changes in heat loss, and heat gain....also inconsistent heat pockets.

Everything in regards, whether it's a race engine, street engine, work engine... car, truck, or tractor....ring gap has a dramatic effect on performance, and endurance.

OK U R right.
Never mind...

[ACmowerguy]

I tend to think it has to be my rings, not the block. Reason being is that the rings were placed at approximately the same location in the cylinder when each was measured, and still there was one that was perfectly fine and the other was .005 out of new spec, but its still in spec for a used ring so I guess it will have to work. I'd buy the OEM piston and rings but they'd cost a minimum of $130, and I paid $60 for the prime line so I'd just be out too much money. The cylinder was bored to Kohler .020 specs, not to the aftermarket piston size nor was it just bored .020 beyond what it was previously. The piston and rings were designed to fit the .020 Kohler spec.

[Glenn M]

The newer Kohler engines have .025 ring end gap.
Having the top ring end gap a little wide, is better to than too narrow. With too tight of a gap on the top ring especially, since it receives more heat than the other rings, it will expand, butt up and break, then you'll have real problems.
If you want it dead nuts, buy another .020 over ring set. If it were me, I'd put it together with what you have, being the second ring is at the correct gap, the compression lose would be minuscule.

[oldsarge]

Do yourself a favor and break it in on Straight 30 wt NON Detergent oil for a couple hours.

[Glenn M]

AC
Are the top and second ring the same thickness and style?

The reason I ask, after reading this, if you swapped the rings they would go along with this quote from Speed- Pro.

" Recent testing has proven that a
larger second gap increases the top ring's ability to seal combustion. This larger "escape" path prevents inter-ring
pressure from building up and lifting the top ring off the piston allowing combustion to get by. Many engine builders
have reported lower blow-by and horsepower gains at the upper RPM ranges with wider second ring gaps. Also,
almost every new car made is using this inter-ring pressure reduction method to lower blow-by and emissions and to
increase engine output".

[Glenn M]

I see that Tulsa Engine Warehouse sells PrimeLine parts. Maybe you could give them a call and see what they say.

[roosamaster]

You have hit the nail on the head yourself. Anytime an overbore is needed, the machine shop should require you to supply the piston that is going into the engine, not just to bore to a "spec.". Since this has already happened, as long as the top two rings are the same (as they may be) use the second ring as your top ring (properly gaped) as this will affect your compression directly, then use to "larger gaped" ring in the second position, which isn't as critical.

Good luck with your rebuild
Roosamaster

[Walt 2002]

I quit using a custom machine shop years ago because, even after repeated complaints, they were boring the cylinder too large. They do this to CYA, ensure rings don't seize.

Now there has been a bunch of posts here about end gaps, saying .025" end gap is OK. I disagree. B&S engines of similar bore size specify .008" min. end gap. I have used this for years, hand fitting, and absolutely no problems. I don't think there is that much difference between a Kohler and a B&S, actually I have been doing that also on the few Kohlers I have done. Heck, .025" is pretty nearly worn out with .035" being replace. By the time .025" end gap rings are seated, the end gap will be .030" or close to it.

I now oversize cylinder bores myself to suit and use .010" oversize rings when installing new rings in a bore that does not need oversizing, hand fintting to as near .008" end gap min. as I can.

Walt Conner