I recently acquired an '86 K100 that had been sitting in an apt garage in Berkeley for the past 10 years. Basically I believe the motor, wheels etc are in decent shape. But the frame has a great deal of surface rust. At the same time I have a K75 parts bike which has the engine and electrics but no tranny or rear end. My goal is to refurbish the K100 and get it back on the road. The K75 is going to be parted out and the engine and parts put away to replace bits on my other two K75's. Looking at the work involved I'm wondering if it made sense to strip the K75 down, store it's parts and move the K100 parts over to the K75 frame which is in better shape, i.e. less rust. So far I've been told that the K75 is a K100 with one less cylinder. I've no idea of the vintage of the K75 parts bike. Any comments or thoughts on how well this might work or if it's crazy?

The front down tubes on the frames are different. Since the K75 engine is shorter, the frame has the tubes angled back more than the K100.

As far as the rust, an afternoon with a wire wheel on a drill will clean up virtually all of it. What's left can be removed chemically or by taking it to a sandblaster. Follow this up with rust converting primer followed by POR15 paint and you will have a frame that will look good for many years to come.

Thanks, that's the sort of thing that isn't immediately obvious to the untrained eye.