Not really Adv, not even a motorcycle! It's an Avia 750 Mk III, a Czech race car from 1956. Take a look under the hood!: http://www.autoblog.com/photos/avia-750-mk-iii/ Is that motor mounted upside down? I'd expect to see some push rods. The motor on the stand isn't quite the same one.
The motor in the car looks like a R90S (note the carbs) and is mounted "right side up". The pushrod tubes are under the cylinders, as the camshaft is located under the crankshaft. These motors are commonly called "Airheads" and were introduced in the '70's. The motor on the stand is probably more current to the '50s vintage car. Someone will quickly identify it, but it is more like a /2 motor with the camshaft located above the crankshaft, and pushrod tubes on top of the cylinders. It sorta looks like the older overhead cam RS motors, but those used a single towershaft/bevel drive overhead cam and not pushrods. Neat pictures - thanks for posting!
I'm not sure why the gallery also shows images of the engine. Perhaps to show the old engine that came out of the car when the new on went in. I'm familiar with how the pushrods went from above to below the cylinders with the /5 series. That's why I expected to see pushrods on top on a '56 car, but you're right, the engine is likely a 70's one, R90S sounds like a good bet. Is anybody building something similar with a current BMW flat twin?
It's not current but, just for fun, how about the BMW 700RS based on the BMW 600 / BMW 700? EDIT: I almost forgot about the GG Quad which used a Oilhead boxer twin motor!
Wow, those are really lovely! Not a boxer twin, but I wish BMW would have produced this: Not sporty, not a boxer, and not in the US, but here's a current model 2-cylinder car: http://www.autoblog.com/2010/07/09/fiat-debuts-two-cylinder-85-hp-twinair-engine-in-fiat-500/
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Great video! Too bad I don't speak German, although I could appreciate the "sports auspuff". I'm glad they allow you to hear the engine a lot. It handles remarkably well for a little old car. It's not quite the same engine as the contemporary BMW bikes, is it?
