Simon e-mailed me regarding this awhile back.
Apparently Motobecane made three variants of the Mobylette?
Our good ol' government decided that the braking and lighting systems on all 1975-1980 Motobecane Mobylettes were not up to snuff, and put a recall out on them.
I know the stopping distance on my 78 is pretty bad, and I'd probably fail a DOT inspection (I guess mopeds and motorcycles have to skid the back wheel on dry pavement in most states)
Some people seem to have motobecane mopeds that run perfectly fine, but just won't go faster than 15-20 MPH. You may have some sort of "wedge ring" in your dimoby clutch (automatic pulley transmission) which keeps the pulley from closing in and allowing the bike to go top speed.
Simon had let me know that there are identifier tags on the bike's VIN Plate that denote if it's an "A" "B" or "C". Plus some motobecanes have smaller throttle bodies on the carb.
If you want to read up on the full details of the recall go to www.carbug.com and search for "motobecane"