There's a guy on the BMW MOA forum who's in the process of restoring a R75/5. Like my story, he bought the bike in rough shape and stripped her completely down - he rebuild the engine, bought a new wiring harness, and when he put her back together, eventually got frustrated trying to get his bike to start.
He brought his bike to a shop but so far isn't happy with the attitude of the owner so he may go elsewhere. A forum member suggested a shop on the East Coast (USA) that specialized in Airheads called The Nickwakett Garage. I checked out his site and found some interesting commentary about the "angles" in grinding valves. I'll paste what I read below - I'm interested in hearing from the collective wisdom here at R65dotorg as to how different or improved a bike can run with the valves ground in a certain way:
CYLINDER HEAD REPAIR
One of my specialties is BMW Cylinder Head repair. I began doing head work at about 14 years of age, learning from my father. As I gained experience, I learned the significance of valve stem to guide fit, valve face to seat contact and the effects of the various grinding angles used. I have learned a fair bit about the metalurgy involved and it's effect on clearances and durability.
Many people speak about three and five angle valve jobs as if some kind of magic results from their use. In fact, the "extra" angles ground or cut on the seats are simply to make the contact area a consistent width and to place the valve correctly. Fourth, and fifth angles-or more-are to improve air flow.