Next project: attaching a “Mr. Fusion” and a flux capacitor.

A BMW Airhead is the bike that you’d want to ride on some sort of time machine journey into the past, because there’s nothing on the bike that can’t be fixed (instead of replaced.) Everything on the bike is electric, not electronic, and even the diode board could probably be fixed with some kind of rare Aztec crystal that you’d have to rescue the high priest’s daughter to get. (Um, there’s a reason I haven’t been submitting my dreams to Genevieve for interpretation: they’re pretty easy to figure out.)

This weekend, I fixed the odometer on my bike. The numbers had been acting bizarre; four miles out of the previous owner’s driveway, and my 51,000-mile Airhead had turned into a 91,000-mile beater. Another minute down the highway, and I was the proud owner of a factory-original showpiece with only 1,000 original miles on it. This kind of wild fluctuation in the value of the bike is exhausting, however, so I decided to do something about it. Plus, the trip-meter was also broken, making the fuel range a matter of voodoo, not subtraction.

Members of the Airheads list sent me some detailed stories and instructions about how they fixed the same problem on their bikes, so armed with their messages plus my 800-page Clymer manual, I unbolted the instrument cluster and opened it up. No green etched electronics inside: just black Prussian plastic and blue Prussian bayonet lamps. Sure enough, the main drive gear (arrowed) had come loose on the shaft, failing to turn the numbers and also allowing them to separate, choosing whatever figure they felt like at the time. I pulled the shaft out, roughened it with a pair of Vise grips, reset all the numbers to zero, and tapped the gear back on.Voila, it worked!

And I still had time to put the instrument cluster back on the bike and drive away before the horde of feathered Inca warriors crested the hill.