This is an unusual way of adding an engine to a bicycle, in this case a folding one. The engine, from a model 28 or 207, is mounted back-to-front and appears to be attached by only the rearmost two engine mounting. I would have wanted to add a strut down from the seat tube, passing under the little fuel tank, to the frontmost engine mounting. The drive is through a very long chain to the left-hand side of the rear wheel. With no normal means of adjusting the chain tension he has added a chain tensioner of some sort, probably a little jockey wheel, to the rear wheel frame strut.
The engine must be running backwards compared to how it would run normally in the original moped. This is no problem for a two stroke engine, in fact two strokes can sometimes almost stall or backfire and start to run the other way by accident, although the timing must be very close to TDC for this to happen. This bicycle must have its engine timing reset to what would be “after TDC” in a normal Babetta to ensure that the engine runs properly backwards. This would require some modification to the fixing of the stator or rotor to achieve the required setting. Pedalling the bike forward will start the engine in the intended way.
Note the Transimo ignition unit mounted just below the fuel tank, and the very neat little exhaust.