TOPIC:

Biltonjim - great find! That's exactly it! I don't understand why this stopper ring (now I know the correct term) is not addressed in the manual or caliper servicing guides. True, perhaps they usually stay in, but I can't believe I'm the only one with this issue having a vintage bike and if they sell them, there must be need for them once in a while.
I am going to reach out to pro restoration shop somewhere and ask them what exactly they use or do to keep this ring in place.
Personally, I would probably use high temperature red Loctite to be on the safe side. The rings are in good shape but everything needed a clean up. Regardless, they are out and need to go back and that's it. Whatever medium used, I wouldn't want it to leak towards the piston, so I will just push it out and clean up that groove where the ring goes from any traces of grease.

Fun removing the old tire with a box cutter knife and a screw driver.

No need for these but just another way.

A bonus - just spotted the original Kawasaki tire balancing weight! Should I make a ring out of it? I wonder how many of them are out there. Definitely a thing for a true restoration purist.

Stan !!! Always cut "Away" from your "other" wrist and....
/ YES - KEEP THAT WEIGHT !
Based on current prices for OEM 1300 parts - That weight is worth at least $15.00 u.s.d. per gram

Scotch:

Stan !!! Always cut "Away" from your "other" wrist and....

Sometimes a picture is not worth a thousand words I see, so a few words of clarification. My right hand is not on the knife but holding a camera!
It's all just a photo shoot set up! Took a few shots to keep that knife jammed safe from falling. Yesss!