Pistons atlas vs commando

I bought a set of pistons for my 750 but the piston rings i have dont fit. The original pistons had a much deeper groove for the oil ring/retainer to sit in and mine is much more shallow. Any idea's? where could i get a set of rings for that???....seems like "low profile rings" isn't on option on any website....

-Dave

What brand of pistons do you have? The early Hepolite Powermax pistons for Commandos had the shallow oil ring set. I don't know if the standard Hepolite pistons for the early Commando also have used them. I'm not sure when they changed to the deeper rings. My '71 PR came with the Powermax pistons with the shallow oil rings. It used to be easy to get the shallow ring sets, and might still be, if you have the right part no. They were a bit more likely to get out of the groove while installing the cylinder, so you had to be careful with them. I had a base for holding pistons in the lathe, so I chucked one set of Powermax pistons up and cut the oil ring groove deeper to match the later rings. That's not a practice anyone recommends now, but it worked ok, and the pistons worked fine in the race bike.

Ken

During my last trip to the USA I bought a set of rings from Rabers Parts Mart, Richard, who is the parts guru, asked me what year it was for, as the Atlas and early Commandos apparently required different rings to the later Commandos. I think Rabers had both types in stock, so you could try them.

I have a lathe also so I could turn them down or get my cnc buddy to do it.............they are powermax pistons btw. What do you guys think is better? Just buying the shallow ring set?...seems a shame as i have the deep 750 +20 ones already......... not sure what the best option is...

Who is Rabers? Im in Canada.
-Dave
Happy new year guys. :mrgreen:

Phoned Rabers....no help at all. Didn't buy the piston rings or pistons from them so the "couldn't help me".....argh.

"You have to send your pistons and rings to us and then we will let you know if and what we can do" HAHA suuuuuuuuuure

:evil:

I probably have rings to fit your pistons. What oversize do you need. James

+.020 how much you would you like for them?

Wouldn't using a set of "deep profile" rings in cut-down "shallow" groeves, cause the rings to be over-stressed from the get-go?

I have one set left. Japanese manufacture. Plain cast iron. .020 OS decent ring from Coventry Supply. $49.00 US plus postage. If you want them PM me your address and I will get them out today USPS priority mail. James

Why would the rings be over-stressed ?? I dont understand.