The Motobecane Mobylette was a fine moped. Not quite as good as the Puch- it lacked the Puch's chromed cylinder- but a solid, reliable bike nonetheless. You don't see as many in the US as you do in Europe, as it was never imported in great numbers during the Moped boom of the 1970s.
But in France they love their Mobylettes, as you can see in this custom example from a French moped site. At first, I thought this had a lot of custom body work, but a correspondent from France and some more research tell me that MBK- the follow-on to Motobecane- produced some very interesting looking mopeds! This is a custom bike in some ways though. The motor features a 15mm Dellorto carb and an aftermarket tuned pipe. The engine is also a production item, though it's a far cry from the typical air cooled moped engine you may be familiar with. See that thing under the tank? It's a radiator. This is a liquid-cooled engine.
Reader Frederic David, writing from France, wrote me a very informative email that I'll quote here:
The manufacturer is MBK, the new name of Motobecane after Yamaha has bought it in early 80's.
Compared to the Motobecane you may have face in the US in the 70's / 80's, it can be considered as a evolution.
Commercial names have evoluted from 50V (the basis for former export to US), then 51V and finally Magnum or Rock racing.
Technically speaking the frame is really similar to 50V. The engine has had 2 major evolutions.
The AV7 engine (the export to the US by the past) 2 strokes, chrome coating cylinder, 13 mm carburator,inlet by piston skirt, 2 inlet ports, air cooled ==> approx 2 HP.
The AV10 engine (Europe market when the 51V appears to replace 50V approx. 1978)2 strokes, chrome coating cylinder, 13 mm carburator,inlet by valves to the crankcase, 3 inlet ports, air cooled ==> approx 2.5 HP.
The MBK512 engine (mid 80's)2 strokes, chrome coating cylinder, 14 mm carburator,inlet by valves to the crankcase, 4 inlet ports, liquid cooled ==> approx 3.2 HP.It is the one of your picture. As you've noticed it is fit with an aftermarket exhaust (french regulation limits mopeds to 45km/h, and the manufacturer choice to limit was the exhaust) expected max speed will be now around 80 km/h.
Thanks very much, Fred.