I don't know what this vehicle is, but it looks as if it is powered by a BMW flat twin engine, possibly from a motorcycle, but perhaps more likely from the 600 or 700 car models.
The fan housing is slightly more visible in the first picture, but the cylinder head is clearer in the second, with the two-piece valve cover held in place by a clamp. Below is a BMW 600 engine, which shows the same features, and the exit point for the exhaust also matches.
I wondered if there might be a connection with the Chrysler Farmobil in one of its incarnations, as that used a BMW 700 drivetrain, but I don't really think so, as the puzzle car doesn't have the forward driving position which all Farmobils seem to have.
