Caliper issues

[mack]

So after my restoration of the 78E, the front left caliper was seeping. It didn't do it all the time. Had me baffled. I took it apart, I was using "tour max" rebuild kits, so I sent away and got K&L. Slowed the seeping down but every once in awhile I'd find a drop or two on the speedo cable. So I took it apart again and cleaned up the caliper itself and checked it for cracks and scratches that might enable the fluid to get past the seal. Nothing. So I got looking at the piston itself. It was a new SS piston so I checked the diameter against the old one and found that it was a few thousands under the original cast one. I knew I had three new cast ones upstairs and dug them out and checked them as well. They were all dead on 1 1/2. I put one in the caliper and put it all back together and bled the system. So far two days and no seeps, so I'm optimistic that poor quality control with the SS pistons was to blame.

[IanDMacDonald]

Dang. One of the HVC ones? Sucks. I used those on my 750 that got stolen. No issues.

[HalfCentury]

Its good to know that aftermarket pistons may be a problem. I have considered buying SS pistions but opted to re-use the stock pistons.

I have rebuilt 4 calipers. One on an XJ650 and all three on my XJ1100. Even though the insides of the pistons become pitted and rusted, I have not seen any rust or pitting on the business side of the piston. I boil the calipers and pistons in lemon juice to remove all of the rust and then dremel wire brush the caliper bore to remove all of the vulcanized rubber and any pitting.

Its a lot of labor, but satisfying to experience properly refurbished brakes.

[mack]

Hvc

Yes these were from HVC. I bought three full sets front and rear for all the bikes. But only one was under sized. Go figure. I have spare sets of calipers for each bike, so I can do a quick swap at anytime, then can take my time in the winter getting around to cleaning them.
50- I have an ultra sonic cleaner that reduces a lot of the work on both e bodies and the pistons.

[BowlingSS]

HVC's vendor for that piston probably has a wider spec than Yamaha or their QA is not very good.

Bill