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Tuesday, March 4, 2014

Gosh Darn It!

Ok, not the words I've really been using...
Rare, "unobtanium" right ATE caliper on the BMW R65
I performed, or I should say, started, the rebuild of the 2 ATE calipers on my '81 R65. The right side, which was the side that was frozen up, came off and came apart with little resistance. After hours (literally) of scrubbing and cleaning, I had a very clean and serviceable caliper that took the rebuild bits – along with the little o-rings from Mike V– just fine. There was some pitting on the pucks, but these were above the seal line so I dressed 'em up and reinstalled. All's well says I.
Then came the LEFT side. I was stymied in minutes. The 2 bolts mounting the caliper to the fork leg loosened just fine by hand, and the top 8mm hexbolt holding the caliper halves together broke loose too.
But the lower bolt was another story. I was initially being careful, as it looked a little rounded by a previous owner, but no amount of pressure using a breaker bar would pry it loose. Hours of liquid wrench, PB blaster, and heat from a propane torch only yielded a severely buggered head. As this head is the one that stands proud, I even tried locking it in a vise and rotating the caliper around it. No joy.
I'm ashamed I let it degrade this far, but it ticked me off that bolt wouldn't give up.
I really think some previous owner musta JB Welded that bolt in there.
In defeat, I'm off to Bombar's Beemers tomorrow to see if it can be tapped out. I need the leprechauns on my side for this one.
What follows are photos of the successful rebuild of the RIGHT caliper:

The right caliper after removal. We need to separate the halves to get in there and get it all cleaned up and working properly, as currently its frozen and none of the moving parts actually move.

Interior view of the same stick caliper
Here are the 2 halves separated. Years of rust, gunk and neglect.
Water buildup in the brake fluid allowed the pistons inside to corrode and stick

Miraculously, was able to remove the pistons from their bores. That thick brown viscous mud is supposed to be clear brake fluid.

Closeup of the inside bore. Not what you want to see.

Here's the piston that came out of it. The outer face is supposed to be smooth and free of rust and nicks.

Here's the same bore after about four hours of cleaning and polishing...

Here's all the bits after a lot of cleaning. You can see the surfaces of the pistons at the top are quite pitted,
but the pistons are no longer obtainable, and the pits are above the seal line, so they'll go in as-is after some
dressing up with a file.

Here's a bit of before and after:

The reassembled caliper, with all new seals, ready to reinstall on the bike

Now, lets hope I can salvage the left caliper...

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