Aftermarket piston rings

Bucko wrote:

Kawboy wrote: …..Since the mid 1960's, Kawasaki has been in the business of manufacturing motorcycles as a 5% of their total Kawasaki Heavy Industries business. They weren't new to the game. The question then is how and for what reason did they have a known oil consumption problem with the KZ1300? Machining practices would have been the same as other models. Piston and piston rings would have met similar standards to other models. So what went wrong?

My theory is that this was the largest motorcycle engine they had built, their first six, and their first motorcycle engine that was water cooled – i.e. I don’t think they knew what they were doing.
If remember correctly (and I often don’t) later KZ1300 pistons had more oil return holes drilled in the oil ring lands.

Now that would be interesting to confirm or deny.

LEFT - 1980 piston. RIGHT - 1982 piston.

So, it's safe to say the 1979 and 1980 had one row of holes, and from 1982 two rows (5 holes each). 1981 - I don't know.

Thanks for the info Stan. Very interesting.
It could be a photo angle thing, but the piston on the right looks taller than the one on the left and the right one appears to have a higher dome?

I positioned the pistons in a way to compensate for the lens distortion, so physically they are not perfectly aligned despite the illusion of it. Regardless, you are right.

The 'dome' is flatter on the earlier model, and nicely round on the 82. The ring groves spacing, bottom profiles, underside, are the same. But if you put them upside down, the 82 piston is slightly taller - because of the rounder profile. I guess that will give a slightly higher compression.

The only other difference is the profile of the lower edge of the oil ring grove. The 1980 has a machined simple flat angle, and the 82 is straight down first, then a similar angled but much shorter due to the different diameter. You can see it go right through the extra holes. Actually, it shows in the photo if you look closely at the right sides of the pistons.

I haven't measured the size of the holes, but all look the same and they all come in fives.

Stan: The oil ring land on the piston on the right looks larger too - or is that just a photo angle thing?

Also, the piston pin location could be higher to offset the increase in dome height to keep the compression ratio about the same.

It's an illusion due to the lens distortion. When you look at the sleeves, the one on the right looks much bigger as well. I just connected both pistons with one pin and they are identical. All the groves and edges align. Judging visually, the curve on the later model makes that dome about 1 mm higher.