nice bike you got there 
Hi there!  I really need the cash for this bike.  I can offer to sell for $185.  This was a $400 bike new, so it is a great deal.  You interested?
185 is still pretty high for me. especially for a used bike. i can go... 140 tops 
If you can pay $155, I will throw in a bike chain, lock, and helmet.  Deal?
you know what? that is a deal. 155 it is for the bike, chain, lock and a helmet
Perfect, thanks!