I'm Lucy, and I'd be happy to answer your questions today. I'm sorry to hear that this happened.
You have the ability to sue for a full refund. A contract requires a meeting of the minds. That means, when you're buying a vehicle, you are buying something that you can register and title in your name and operate as a motor vehicle. If it's got a salvage title, you can't do that. A salvage title needs to be disclosed prior to the sale. So, if you agreed to buy a motorcycle that you can drive, and he agreed to sell you one that is salvaged, there's no meeting of the minds. The contract fails.
The general default rule of as-is sales doesn't apply in this situation. California law also requires that a seller provide a smog certificate with a vehicle when selling it (including motorcycles), and he can't do that if the vehicle is salvaged. Cal. Veh. Code, Section 5751.5.
You can file a lawsuit in Small Claims Court for a full refund of your money, plus your filing fees. You will be required to return the motorcycle if you win the case. You do not have to sign the bill of sale to complete the purchase.
Here are the forms and instructions.
If you have any questions or concerns about my response, please reply WITHOUT RATING. It's important that you are 100% satisfied with my courtesy and professionalism. Otherwise, please rate my service positively so I am paid for the time I spend answering questions. If you are on a mobile device, you may need to scroll to the right. There is no charge for follow-up questions. Thank you.