650 piston rings

[jimhickcox]

Since I already have my 550 engine out of the bike and torn down to swap out elements of my transmission, I am of course attempting to also drop on a 650 top end. Why just fix something when you have the opportunity to cause new problems as well!

I've read all the threads (or at least a dozen) and I think I know most of what I'm in for. Figuring out a new base gasket is my biggest worry, but I've printed out other folks' measurements and I'm prepared to do a squish test when I get there.

Right now I'm waiting on an oil seal to start putting the bottom end back together, so I started futzing with bits of my top end, and while I was cleaning my pistons I took a second to check out the rings that I'd bought. Some folks on here seem to have had a good experience with the cruzinimage ones, although others say to stick with OEM. I couldn't find much in the way of OEM, just cruzinimage (https://www.cruzinimage.net/2017/08/...rings-include/) and things like this on ebay that could be anything (https://www.ebay.com/c/671764310). I got the cruzinimage ones, and looking at them today I got confused. The rings that were on my pistons are, I assume, the originals, and the top two rings look totally identical. On the cruzinimage replacements the top two rings have the same OD, but different IDs. Does anyone know anything about this? Are they trash? Would those ebay ones be better? If they're not trash, do you know which one goes where? They came with no literature at all.

Here are the new ones, squeezed closed. You can see the varying IDs.
PXL_20210311_002340230.jpg

I can only attach one file per post so I'll put one up of the old rings in a reply if it lets me.

[jimhickcox]

These are the ones that came off the piston.
I'm holding them slightly off from one another so you can compare them, but their ID and OD are the same.
PXL_20210311_004832045.jpg

[Chancho196]

Is the wider one of the two the same thickness as the originals? I'd personally measure ring gaps of the original rings in your cylinders and see how bad they are.
When I did mine, there was no visible wear in the liners, and the ring gaps measured ok. It's done a few thousand km's now and doesn't burn a drop of oil.

[jimhickcox]

outside silver color is
install to top slot and
black is install to second slot.and make on topI'm working in a borrowed space so I won't be able to get in there and measure for probably a week or so.
I did hone and measure my cylinders and they're hardly worn at all, so I probably could have gotten away with using the originals, but of course I snapped one while I was taking them off.

Mitsuo from cruzinimage says this about the rings:
"outside silver color is
install to top slot and
black is install to second slot.and make on top"

That gives me some guidance, but I'd feel a lot better if I heard a reason why they're different than the originals.

[GregT]

Current pracise is to use a narrower top ring. I'd suspect that in that size Cruzinimage couldn't source a wider one.
I'd check the ring groove side clearances before installation but if they're within spec, I'd use those rings.

[jimhickcox]

I'd check the ring groove side clearances before installation but if they're within spec, I'd use those rings.

Good to know. Thank you.