I know a 550 tank won't work without customizing a seat and a tank mount, haven't tried a 750 tank on a 650, what's the plan ? How will you get this to work? and what is the look that you're going for? Just wondering.
I'm not wild about an angled tank and seat that is '80-82 650, I like the classic straight lines of the 500/550/750 or 79 650 and have found it easier to obtain this classic look on a classic 550 frame ,over cutting the 650 frame.
Do you know something that I don't know? I'd like to know of another way that would work
(if that's what you're doing).
I have to agree with rb550four as to the aesthetics of the 80-82 650 frames -- I own one. I think Honda was definitely going for a cruiser design. It almost feels like a soft tail chopper. The 550 tank will not work. I don't know about the 750 either. you may need to cut the bottom off the tank and fabricate your own tunnel and mounts.
I suppose it depends on what design and function you want to achieve. If it's a chopper, cruiser, bobber, that frame will work fine. If you want something more like a tracker, café, etc. you may want to do some frame alternations to the rear top rails. For me, I am scavenging the motor for possible later use (right now the motor is in mothballs in my storage space) and I may save the frame for some crazy project in the future (since it is titled).
That said, the CX500 plastic maggot has the same frame dip (where the seat is) and plenty of people have turned them into nice looking (but slow) rides.
