Dont wait on him to call, pick up your phone and call him, heck I would have offered him $225.00 when he told me someone else was looking at it, and if he bit you would have still got a good deal, the engine in the box looks just like the engine on a 52cc harbor frieght gas post hole digger/drill, I have heard those are very good engines for the friction drive set ups, the BMP drive assy. will run about $129.00 + shipping and the new egine can be bought for $119.0 + shipping looks like a $50-$75 bike and then there is the engine thats on the bike and if it is worth $50 you have a total value there of $350-$400, thats a dang good deal....I'd call him back soon, just to be sure.
Good luck