Does anyone know the changes between a /5 main frame and a /6 main frame? Other than the battery mount bottom piece and ears, and the tab for the steering friction plate. Can I swap everything from a /5 to a /6 frame without major modifications? It appears the horizontal crossmembers at the rear are a larger diameter. thanks, dan
I believe everything will swap right over. I think (sort of a dim recall on this) the only real difference between the /5 and /6 was rake angle, but that's nothing to worry about.
I believe that at some point they fitted a second tube up the middle of the main spine presumably in an attempt to strengthen it. Mine has this double wall tube.
I have read that in glossy magazines but BMW's frame jig test all airhead frames. They all have the same rake. /6? ?6's were constantly changing. It probably depends on what year /6. You at some point got the doubled tubed backbone, the extra cross brace under the steering head and a lot more and bigger gussets. By '81 the frames were a lot stiffer and heavier.
this frame is dated 6/74. Sounds like a good strong frame to hold all the torque from my R50/5 power plant
As you surely know the rear sub frames changed from the short wheel base to the long wheel base. The late 1973 long wheel base sub frames are a double tube cross brace arrangement and stronger than the 1974 stamped steel cross brace arrangement. When I cobbled together my 1974 framed sidecar rig I sought out a 1973 1/2 rear subframe for that additional strength, plus my old QSL solo seat needed the arrangement for the mounting system.
yes, I am keeping the short wheel base subframe and swingarm. Did you weld on the tab for the old front end friction type steering dampner?
I ended up with a modified dual disc BMW 60's Earls front end... lengthened a /5 damper rod to fit the Earls, then had to get "creative" for the lower damper pieces to mount.
