Easiest way, change your BTC for cash and give that to him. Certainly in the current climate no one is going to want to accept bitcoin for goods.
They're not accepting Bitcoin if they use a payment processor. They're receiving dollars sent using BTC as a payment rail. In quite a few places people would rather stay away from banks and let a payment processor handle the conversion. Less potential for the bank getting arsey.
Yes, but if you convert it to USD then you are cutting out at leat one or two middle men. Someone is going to have to pay for the conversion. This means you are going to get a better exchange rate between your BTC and your bike.