Powerdynamo brings new ignition & light 
to your vintage motorcycle



Technical Help



At many engines (such as DKW, BMW, Aermacchi) there are differences in crankshaft diameter (17mm or 20mm). This requires different rotors in our systems. There are unfortunately confusion among customers.
Therefore, here is a brief presentation on the example of DKW (although in the case of BMW and Aermacchi is no different).

The 17 or 20mm are always based on the the bigger end of the cone, so that part of the crankshaft pin which goes cylindrical in the ball bearing. Since there is a shaft seal it may not be possible to measure at the 20mm end, but it's close to it, and sufficiently far away from 17mm.
Even if, as in the illustrations, you'll measure little greater diameters as 17 or 20mm it is always exactly 17 or 20 because of the ball bearing.

Pictures could be enlarged by clicking
At the small end of the shaft this is naturally much less than 17 or 20mm. The smaller diameter depends on the length of the shaft. So it is different on different models. Here at teh DKW models it is approx. 14 or 16mm.