I’m taking my 1977 BMW R100/7 out of mothballs this year. And, by “mothballs”, I mean “sitting outdoors under a tarp for a year”, which is the motorcyclists’ equivalent of starving your dog. However, having a baby seems to be the one circumstance when this kind of behavior is forgiven — once. As long as I do some good, solid wrenching on my bike in the next couple of months, the Airheads might let me off Double Secret Bike-Poser Probation.

After a year outdoors, the brake lever pulled all the way back to the handlebar, which is a bad thing. Topping the reservoir up with fluid didn’t help. When I got the tank off to have a look at the master cylinder, I saw that the piston end was weeping brake fluid. Brake fluid is nasty, corrosive stuff, and you want all of it INSIDE the cylinder where it doesn’t eat your paint. And, you know, where it can help stop the bike and stuff.

So I ordered a rebuild kit from Bob’s BMW, and while I was waiting for it to arrive, checked out the instructions for rebuilding the cylinder in my Haynes workshop manual. I found this:
What the hell is this? What kind of workshop manual gives you detailed instructions for removing the part, then rapidly runs the white flag up the pole? Note that this activity is flagged with three out of five wrenches. Apparently, four of five wrenches means “summon NASA”, and five wrenches means “bury the bike and hope that future civilizations with superior technology possess the means to fix it.”

Also note the helpful advice at the end: “Make sure that you buy the right size of cylinder!” Yeah, THANKS for that parting shot. “Make there are no thunderstorms in the area when you dial the phone!” I wonder how many wrenches Haynes would assign to the act of opening the box the new cylinder comes in. “Have an adult help you open the box; paper can give nasty cuts!”

Not that I think I can do everything on my bike. Lubing the drivetrain splines seems to be the wrenchers’ equivalent of crossing the equator for the first time, and my cheeks are still innocent of tar. I’m still in the “change the oil and poke fearfully at the fork seals” stage. But I’ll be damned if I’m gonna let some half-assed limey teabag how-to book command me to meekly submit my cylinder to Yuppie Central for an overhaul (the waiting room of the Devon BMW dealership is filled with lean, rapacious-looking lawyers checking out the new BMW models. Lean, rapacious-looking lawyers that, like me, do not know how to lube their drivetrain splines.) Hey, books can tell us how to knot a bow tie, right? How hard can this be?

Kate’s dad Bob pointed out that Haynes is notorious for simply reprinting the text of the original owner’s manuals delivered with the bike. Fortunately, my Clymer manual, which is easily five times the thickness, displayed no such dithering in the face of the enemy. In fact, I’m pretty sure you could assemble a space shuttle from a Clymer book.

So I got the piston out and had a look. There was some weird clear plastic wrapped around the piston body, which is a bit of a mystery. Fortunately, any problems with the old piston were moot, as the rebuild kit contained a new piston in a cheerful shade of anodyzed green, and a couple of rubber seals that require some kind of three-armed proprietary BMW assembly awl to stretch over the rings in the piston and put in place. I used fingernails and loud profanity, and shot the rubber rings across the garage several times (lose a single ring, and your spiffy fifty-dollar rebuild kit is now a collection of funny-looking table shims), but finally managed to get everything together. Whew!

Here’s a picture of the piston that I took and posted to Flickr, in hopes that some wise member of the Airheads community would know what the mystery-plastic was in there. So far, about a hundred views, but nobody wants to offer an opinion. Hmm, maybe Haynes was trying to shield me from a terrible secret.