I am in the process of pulling apart my Moto G.A.C. NTT50 DX Cross, which is equipped with a licensed duplicate of the Motobecane D55 motor, and wanted to catalog some of the process as there isn't much info on these stateside. This bike was Licensed to Moto G.A.C. (along with pretty much the entire line up at the time) for production and resale in Spain.
Here's a great site for some history on Moto G.A.C. and coverage of the models they made.
Here's the bike as It sat prior to getting it to back home. It's a 5 speed, 49cc shifter with pedals that rotate and index to become passenger pegs. COOL
Upon getting it home and getting it running, there was a pretty solid grinding/whirring noise when it was running, I had hoped that getting it to loosen up after sitting and running fresh oil would clear it up but no luck. So, I decided it must be the main bearings (as it occurs whether in gear or not, and followed RPMs) and pulled the motor.
Fairly easy. Single chain, two wires for the entire system, and the carb. While this has a SHA intake on it, either the factory or someone else made a custom shim to run a PHBG 15 on there, which was actually running very well.
Here's a shot of the ignition side. Standard Novi, except produced in Spain. The red cap is the chain oiler cover, and the cast bracket that is attaching the pedal shaft to the frame is a stabilizer/pawl setup for starting the bike.