View Single Post
Old 04-29-2017, 03:37 PM
3Phase's Avatar
3Phase 3Phase is offline
XS-XJ Super Guru
Join Date: May 2008
Location: Simi Valley, CA
Posts: 5,465
Originally Posted by skids View Post
I thought standard sized ring sets were unobtainable.
I think Yamaha may renew/reorder parts on their own schedule and the prices change with another schedule that's similar to George Carlin's infamous "Alimony Dart Board."
For example, XJ1100 air filter prices were totally insane last year but now they've gone down and they're just ridiculous.
Maybe they'll get a new batch of starfish washers in for less than $100 a piece.

I dug up some older piston rings to check with my spiffy new Harbor Freight digital micrometer and found the rings I bagged up from the 100K mile + '79SF engine that was in "Bush".
The old Top and 2nd ring are both almost the same thickness and width even though the 2nd ring is cast iron and the ring groove is cut for a thicker ring.
I have no idea why but all four sets that came out of that engine are the same.
It must have been a very exciting time for that poor cast iron ring.

The older Top rings had a mark to show wich side goes up instead of the letters used on the later model rings but the mark on this ring doesn't show up in any pictures because it's been worn down.
The XJ spec. calls for a Top ring 1.2 mm thickness and the side clearance in the early 2H7 and later 3H5 piston ring grooves supports it.
This isn't bad wear for over 100K miles.

The XJ spec. calls for 3 mm width.
If the older rings were originally closer to 3.08 mm wide then at 2.79 mm it's lost almost 0.3 mm.
If the older rings were closer to 3.01 mm then it's only lost about 0.2 mm.
Trying to get a consistent measurement for the ring width with that little ball adapter on the micrometer is harder than Chinese arithmetic.

It's a bummer that the only official chart that gives ring dimensions is in the XJ1100 factory manual after the ring design was changed. The XS1100 manual only gives ring end gaps and side gaps with no dimensions.

I'm going to measure and photograph one of the official Yamaha 3J2 ring sets before I put the pistons back in the XJ engine, then I can compare the new Yamaha rings with the new cruzinimage and old-style OEM sets.
-- Scott

1982 XJ1100J: "Baby" SS Brakes, '850 FD, ACCT
1980 XS1100G: "Columbo" SS Brakes, '850 FD, ACCT
1979 XS1100SF: "Bush" W.I.P.
2018 Heritage Softail Classic 117 FLHCS SE: "Nanuk"

Last edited by 3Phase; 04-29-2017 at 03:42 PM.
Reply With Quote