I often have the opportunity to hang out with "bikers" and they all (still) call them "rice-burners". As far as I know it originated from early Japanesse motorcycles which burned rice-alcohol, but clearly Harley owners use the term with quite different *affections.

A "crotch rocket" is a specific motorcycle design, originally for racing, where the rider is bent over forward in an effort to distribute weight evenly between the front and back wheels and add speed through aerodynamics.

A "Rice rocket" would be a Japaneese racing bike, just like I've heard BMW's called "Brat rockets" and Ducatti's called a "Pasta rockets". If the Norwegians made a racing motocycle you could bet I'd call it a "Herring Rocket"... or sump'in.

There's a whole subculture of "ricing" one's vehicle similar to "hot rodding"... not very mainstream 50 years ago either, but.