Wildguzzi.com
General Category => General Discussion => Topic started by: TDF on May 23, 2025, 09:08:52 PM
-
Had the cylinders on my 44k mile V7 sport nikasil coated to match the original pistons. When dissasembling the motor, I haven't found any evidence the engine has ever been apart. Started reassembling tonight, and was struggling to get the piston with new rings on it in the cylinder. The three compression rings would go in smoothly, but the oil scraper ring was putting up a fight. So I backed off and started measuring, and here's where the confusion starts.
The original oil scraper ring was a ring only. The new one from Crusty cycle has the expander spring under it. I didn't think too much of that initially, but once stuff wasn't going together I started measuring closer, and there appears to be some clearance issues. The groove for the oil scraper ring in the piston measures about 0.155" deep, the original ring measures 0.133" thick, the new ring with the spring is 0.162" thick. No way am I fitting the new ring with that expander spring under it in the cylinder.
Anybody ran into this before? Every website I can find selling the rings for the V7 sport shows a ring with that expander spring under it. It's an 82.5 mm piston, and I got 82.5 mm rings. I think my pistons are original but not 100% sure on that. Am I looking for a special oil scraper ring? Can't seem to find new 82.5 mm pistons anywhere, and I had Millennium size the nikasil coating to the original pistons. Not sure where to go from here.
Photo is from MG Cycle as their pic was clearer, but the rings from Crusty Cycle look just like this.
(https://www.mgcycle.com/images/atrex/14060700_01.jpg)
TDF
-
If there is a competent machinist around, it used to be common to recut ring grooves if a ring was unobtainable.
-
Thought about that, and my youngest brother is a machinist with a well equipped garage, so I'm sure we could pull that off. I've heard of widening ring grooves, but I'm a little leary of deepening grooves as I don't want to weaken piston too much. I'll have to do a bunch more measuring and see what I think.
TDF
-
You wouldn't be removing much material from the piston if I understand correctly. I would measure to see how much material would be left after the machining. In the aircraft shop the boss recut pistons cut often, there were no replacements being made. We more often ground rings to fit also but only for thickness. We had a supplier for all sorts of rings but the boss has passed on so I have no way to find the company.
kk