After cleaning out and overhauling the under-tank master cylinder a couple months ago, I checked on it once a week and sure enough, it was leaking. Not leaking a lot, but any amount of brake fluid outside the brakes is Not A Good Thing™. So with another Wunderlich order needed for various other service parts discovered in need of replacement, had to hunker down and spend the $75 US on the rebuild kit.
Straight forward as before. Helpful, as always, to follow along with Brook Reams documentation of the procedure, mainly to confirm that the second seal on the piston is, indeed, very tight to get on and I was very worried about breaking it. Biggest seal stretch I’ve done yet.
Took the opportunity to re-hone (emory and 400 grit sand paper on a drill bit) the cylinder bore. Put a crush washer on the switch screw for good measure.
One of the more satisfying customer service experiences has been buying from Wunderlich and they really came through last week. BMW part #34 31 1233309, aka the “rod”, the little elongated pill-shaped external rod between the piston end recess and the cable-actuated arm, was long missing from this bike (previous owner had gone master cylinder on the bars in the 90s) and the “rod”, as far as I can tell was last available then, too. Miguel at Wunderlich heard my woes, and apparently a co-worker of his did, too, and lathed me one up himself over the weekend and mailed it with my order.