With the impressive results folks are having with the newer twin-ring Ryobi 31cc vs the older single-ring versions, plus the fact that most of the "pro-grade" industrial engines (e.g. Kioritz, Echo, Zenoah, etc.) all have dual ring pistons, wouldn't it be a fairly simple hop-up to machine an extra groove on a single-ring piston to accept a second ring? Afterall, larger automotive engines typically have several rings - some for compression and some for oil control.

It shouldn't be all that difficult if you have access to a lathe, should it? Has anybody tried this?

Some pistons have a little extra meat where the ring or rings are and as you move down the skirt it gets thin pretty fast. On the Ryobi I dont know, If there is enough material there it should be a pretty straight forward modification. A fixture or something to hold the piston might need to be made up to keep from crushing or scaring the piston in the chuck of a lathe.

Adam

I thought about doing this on an old single-ring small Ryobi (26 cc -- not the 31) and decided there just wasn't enough space above the wrist pin hole to squeeze one in. On other engines this might be doable. I too would be interested to hear if anyone has done it...

Why couldn't you just order a new 2-ring piston and stuff it in the old engine? Unless the pin diameter, bore, stroke, shape, and weight are different, it should work.

Doug

It's going to take more than an extra ring to get the power of the old motors up to that of the new one. The new cylinder has a larger more "D" shaped exhaust port that is unbridged. The best that I can remember, the transfers ports are a little different too, but don't quote me on that, it's been a little while since I've had them apart to compare. I really can't see why the guys want to buy the old refurbished motors from Harbor Freight when you can get a new twin ring from Wal-Mart for around $69. There is a big difference in power between the old one and the new one.

Actually, I really had Poulan chainsaws in mind. With Ryobi twin ring refurbs going for $49 a pop, it really doesn't make much sense working on the old ones. The bigger Poulans (46cc, 50cc, 54cc, etc.) are still all single-ring and might just benefit from a second ring.

Volfy, maybe you can find a dual ring piston from a different engine/make that fits or can be made to fit? you might also find something with a taller crown to allow a compression increase. talk to some long-time saw shop guys, if it's a possibility they would be the ones to know.

dave