From 1981 till 1983 Honda produced a tiny motor scooter known as the Motocompo. The scooter was designed to fit in the storage compartment of Honda's subcompact cars. The storage space required for the Motocompo was reduced by engineering in a retractable seat and handle bars. This 1:12 scale papercraft Motocompo was designed by Yasu Tanaka of Japan and comes in three colors: red, yellow and white. The templates for each are available here.
In 1974, American motorcycle daredevil Evel Knievel attempted to jump the Snake River Canyon in southern Idaho in a vehicle known as the "Skycycle X-2". While the vehicle did have two wheels, it was really more rocket than motorcycle. This papercraft version of the X-2 is the work of model rocket enthusiast, Wayne Hill. The model is intended to be used in model rocketry, but I think it would make an interesting bookshelf model as well. The two part template download is near the middle of the page here.
You don't see a whole lot of papercraft of Marvel Comics' Ghost Rider around. That's probably because it's tough to do all the flames. ^^ Joe Apodaca, however, has managed to do a pretty good job with this hako version of the Spirit of Vengeance. He gets a gold star for including a chain, too. ^^ The motorcycle and the figure are two separate models. Templates are available here.