This is a good first step. If the seller agrees to a partial refund acceptable to you, you get the cash from him, not the CC company or paypal. It's to his advantage to do so, because if paypal decides not to honor the complaint, the CC likely will, and one way or another the entire amount will be coming out of the seller's hide. It'll be cheaper for him to reach an agreement with you. This is why it is important to stick to just facts-- you want him to come to this very conclusion. Decide the minimum you will accept. Good luck.

+1 on the randomness of shipping quality via ebay. I don't buy bikes thru there any more after two bad expereinces; I prefer to find them locally. Plus, I have too many bikes already and don't need to be buying more.