Please take a quick word of advice from my past. I do have FIVE lawyers in my family and they all put in there two cents . First there are many limited liability contracts on the net for free ,find one that you like and use there boilerplate as a foundation for sales contract. Second I never sell a whole working bike ( whats this guy talking about???) in most states you can privately sell a bicycle w/o following all bike dealer laws and reg. , but if you represent yourself as a dealer then there a lot of red tape. Long story short , i build ,road test , even lett the coustomer ride bike and then before sale just remove spark plug! Simple easy and covers your butt. However make sure you list in contract that bike was sold as is and nonfunctional. Just tell your cus. What plug to buy ,or sell it seprately on diff. Day. They need to know how to check plug anyway so lett them put it in after they sign sales rec.
This may sound silly but it is based on the laws re:bicycle sales for most states.
One last thought , leave all the stickers and reflectors on bike ,thats how it was legal for your dealer to sell to you. Lett the new owner pull that stuff off if they want.
Following this procedure (in most states) you might as well be selling a paper weight with wheels . Hope this helps .
P.s. I didn't include a copy of my liability wavier because it needs to be unique to your operation , so if you copy one from net or other source change wording enough to be orignal ( just opening line or add something at end)