Monday, December 30, 2013

BMW R75/5 Headlight Reworking

Recently bought a 1971 BMW R75/5.
It's in pretty good mechanical shape. Though, I haven't ridden it more than 100 miles yet. These old bikes always offer something mechanical to deal with. I am slowly working through some cosmetic stuff. The ignition had been replaced, and the headlight was electrical taped on. I wanted the vintage nail key look, not a big ugly key sticking out.
So, those are the first things I wanted to deal with before moving on to sanding, filling, and painting. I bought an ignition upgrade from Rocky Point Cycle. Once I got it I realized my headlight shell was in worse shape than I thought. It is supposed to have bendable tabs for holding the ignition up. See PenForHire's resto of a 1973 R75. He did what I want to do with a new key. I'm way too cheap to just buy a new headlight bucket ($350!)

Well, I had to create some way of holding the ignition mount up on the underside of the bucket. I decided to weld a ring into the bucket that would have holes aligned to holes I tapped into the mount. I drilled out a 3/4" hole into the center of a washer. Then, I drilled clearance holes for 8-32 screws on the washer. I know; it should be metric, but I didn't have the list of drillbits associated with metric taps. I center-punched these holes onto the ignition mount from Rocky Point. I then drilled and tapped the holes on the mount. I tack welded the washer on the underside of the bucket using a MIG setup. It was pretty ugly. So, I finished the job with JB Weld. I still need to grind down the tack welds.

It's still really ugly, but the Rocky Point mount now can be held onto the bucket. One word of caution, if you're removing your headlight bucket be sure to label every wire. I used blue painter's tape and a Sharpie to make sure I knew what connects with what. Much of my electrics had been toyed with in the past. So, the wires weren't all color coded as the originals were. I'm going to smooth the welds out tomorrow. Then, I'll sand it. I've ordered POR-15 to reline the tank before sanding and painting it. I've had good luck with the POR products on two other tanks. The bike has been repainted already as indicated by the tape pinstripes (ugh). I plan to paint and pinstripe it myself. I'll post more on the changes as they come.


Kramer said...

Short wheelbase swing arm, probably a 3.20 rear-end? The R75 motor was the best of the flat twins, perfectly balanced. Loved the old "nail" ignition switch...

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