With 2 550's under your belt, and your current 750, I would say that you are definitely not lacking in the ability department. In terms of doing a 650, I would say why not? All you can do is learn more than you already know.
Now, in terms of this bike, I agree with bollingball, no where near enough info. The only 2 positives I see at this point are that the frame/swing [sewing, really?] arm have already been powdercoated, assuming he didn't mess it up putting the motor back in, and he has what looks like a Benelli tank [I'm a fan]. I would have to go through the normal list of questions before I would even go look at it:
- Does the motor run?
- How many miles are on it?
- Is there a title?
- Says "almost all parts to complete" what does he/she know is missing?
- How long has it been their project, been apart and/or since they worked on it last? [the amount of parts they actually have, and condition of them are directly dependent on this question]
With those basic things out of the way, and it still sounding decent, going to look at it should answer anything else you wanted to know.
Good luck, definitely has the possibility to be a nice project.
