This is not a simple question because driver's licenses are issued by states, not by the federal goverment. As such, there are basically 50 sets of rules about whether your foreign license is recognized by any particular state you happen to be driving in and what restrictions or limitations might apply.
I've heard the general rule of thumb is that if you have a valid foreign driver's license that it will be generally accepted in the US. And I don't think any states in the US issue motorcycle licenses tiered to displacement, although some do not require a separate motorcycle endorsement if you riding a bike below a displacement threshold. Whether your use of your foreign license makes you subject to the restrictions of this foreign license? I suspect you'd get 50 different answers to this question if you asked each state about this.
Some say that getting an international driver's license is a good idea, especially if you license is not in English.
Most just "wing it" and hope for the best. I think in your case, the key thing to check is what license requirements are for bike rental agency you're planning on using. I'd also ask a lot of questions about insurance.
If you're buying, that's a whole nother can of worms as vehicle registration and titling are, once again, handled by individual states. There are several threads in this forum discussing this.
markjenn screwed with this post 02-17-2013 at 12:57 PM