i'd say at least 2 pints minimum. you'd be better off getting a quart to be safe.
i know a bike doesn't sound like much but thats the bad part.... you lose alot in the overspray.
for example, i used to paint sandrail frames for a buddy of mine that was building them. it took a little over a quart per coat since most of it was in the air and on the shop floor with it being all pipe.