Motocross history is filled with examples of creative ideas that were heralded as groundbreaking, but, because of the rapid rate of change in development, sank into the swamp of forgotten technology. Although some are best left abandoned, others were truly innovative (if not ultimately successful). MXA loves to reveal motocross’ tech trivia. Do you remember this idea?  The Montesa ball-bearing rubber petcock.

If there was one constant in the world of motocross bikes, at least up until fuel injection made them obsolete, it was the gas petcock. In the days of carbureted two-strokes, especially the Amal and Bing days, you could not leave the petcock open or you ran the risk of filling your bottom end up with raw gas. Thus, every bike worth its weight in gold came with a simple on/off petcock. The vast majority used the same basic design—a simple switch that opened and shut the fuel line by turning a lever. Innovation was uncommon. Perhaps BSA’s guillotine-slide petcock could be considered unique, but it wasn’t an actual improvement. New ideas were few.

That didn’t happen until Spanish brand Montesa blew out the jams with the infamous Montesicle petcock (using them on the VR, VA and VB models from 1973 to 1978). Oh, don’t get us wrong; Montesa didn’t call it that in their fancy advertising brochures, but the source of the name became obvious as soon as the Montesa petcock was used. The Montesa petcock consisted of a molded rubber tube with a steel ball bearing inside. To turn the gas on, you squeezed the rubber tube to squirt the 1/2-inch-diameter ball bearing out of the way of the fuel flow. To shut the gas off, you squeezed the other end of the rubber tube to move the ball bearing over to block the flow of fuel.

It was almost inspired. Almost! The problem? Smog ate the poor-quality Spanish rubber, and the ball bearing would come flying out. This means that today most vintage and museum-quality Montesas are missing their very rare, original Montesicle fuel petcocks.


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