I seeking some info or advice. Smack upside the head possibly but here's the situation. I have Galfer wave front rotors on my 919. My VFR750/F3 front wheel is at the shop being coated. I would like to have some sort of a hub adapter to mount the 9ers discs onto the smaller wheel hub. Is this doable or dangerous?
+1 for putting the proper rotors on the wheel, one less thing to go wrong. You most likely won't be able to recover everything you've invested in the rotors for the 9er but you could probably recover a large portion of it
This is not rocket science, but many of the same engineering principles apply. I know: been doing it for practically my whole life.
In this case it's pretty simple, that is if the rotor carrier has a shallow enough dish to fit between the wheel and center on the calipers -- the most important part is sufficient space between the mounting face on the wheel and rotor carrier for a proper adapter, essentially an accurately machined aluminum washer with two bolt circles drilled into it and a register for the rotor. Can't give you specifics for obvious reasons, but I think you get the idea. Use 7075 T6 51 from a known source and you're good to go.
On the other hand if the dish is too deep and there is no room for an adapter things get more complicated, requiring machining the wheel or making a new carrier. Frankly, if it was mine it wouldn't be worth doing. On the other hand if someone came to me wanting it done I'd say "no problem, but it won't be cheap." and do it.