Another one of my back burner projects is a cover painting of the Marvel character, Ghost Rider.
In preparation for this I built a very quick model of the bike.
I based this on a broad range of references from the comics. Sometimes the bike is drawn quite fantastical and sometimes more conventional, it just depend on the style of the artist who's drawing the strip at the time. My favourite had to be the version with the evil skull face plate and I took my lead from that.