www.b50.org

I'm rebuilding my B50SS wheels and have some questions.
1: I'll probably use RAL 9006 two pack on the hubs and brake backplates. Should I use an etch primer to help it stick to the alluminium or will an ordinary 2 pack primer do?

2: The standard rims are 18inch WM2. Could I fit WM3 without any chainline or fork clearance problems? I'll probably use Rolltru or Valtru stainless rims.

I think it's still wise to use an etch primer on Alluminium even when using two pack paints. I'm pretty sure they use etch primer at work when using two pack on Alluminium.
I restored and rebuilt a conical 8 inch brake front wheel recently using Valtru stainless spokes and rims. I used etch primer on the bead blasted drum and brake plate, although I didn't finish with two pack paint, I used Wheel Silver spray cans.
After a final coat of clear laquer the drum and brake plate then whent in the oven for 30-40 minutes at 100 degrees C. As for the rim sizes, I'm not sure about the front, but my 250 & 500 Victors are fitted as standard with a rear WM3 rim which does not cause any problems.