Motobecane port database
Motobecane mopeds, like many other mopeds, were produced with a series of speed ratings. It is generally accepted that there were 20, 25, and 30mph versions, but there is much speculation as to how these models are classified. Some state that the speed is designated on the front VIN tag, classified as A, B, or C. A counter argument states that that system varies from year to year. Others claim the model type can be determined by the shape of the fins on the cylinder. Some are simply referred to as "fast" or "slow". A new theory proposes the cylinder speed is simply stamped into the side of the cylinder in a "CSxx" format, where CS30 would designate a 30 mph model.
Whichever persuasion you follow, it can be agreed that the speed rating of the bike is determined by the cylinder type. Since, as of now, there is no direct correlation between the cylinder types and different systematic namings, this page is dedicated to collecting and documenting of portmaps from Motobecane cylinders. With this collection of port diagrams, riders can compare their portworks to others to get a good idea of where they stand. This page is meant to serve as a reference, not to prove or disprove any particular theories.
Below is a list of documented port maps from various cylinders, submitted by their owners. Each diagram provides the year, model, length and width of each port, the vertical distance from the top of the cylinder, as well as any cylinder designations. The measurements were all asked to be taken within +/- 1 mm of accuracy, but the accuracy of each drawing can only be verified by the mapper. The only map I can personally account for in terms of accuracy is the diagram mapped by S. Pamboukes. The diagrams are catalogued chronologically.