The financing deal the dealerships will offer is done by Household retail, who finance.. well just about anything.
Its not a bad deal, if you can handle large payments, and can guarantee that you will never ever be late on it. You get a low rate, and 2 years to pay it off in. However if you have to take longer than that to pay it off, or god forbit if you are late on a payment, your interest will jump to an absurd 18% or something like it. If you find yourself in a bind and cannot make the payment you need to, make the minumum on time. Also, dont be fooled by the less than $100/mo payment crap. Pay it off quickly. Bikes tend to get wrecked and totalled pretty quickly (not just the riders fault, there are cages on the streets too) and no one wants to get stuck paying for a bike they cant ride anymore.
If you are scared off by all they ways they can screw you, go with you local bank or credit union. It will cost you a touch more in interest, but you have a better safety net.
Also, do not put gear/parts on your dealership credit card. While bikes get a great interest rate, everything else does not.