Powerdynamo brings new ignition & light 
to your classic bike

 
Changing system polarity from positive to negative ground
Problem Quite a few older motorcycles had electric systems with positive ground. To the old parts this did not matter. As soon as you put in electronnic parts it becomes a problem. Electronics do not like plus to gound and will get destroyed.
Solution
 The solution is quite simple. You reverse polarity of the system in 2 quite easy steps (all to be done before you install any electronics !)
Step 1

You disconnect the battery and reconnect it reversed. That is you connect the minus pole to the wire that leads to the engine casing / frame and the plus pole to the wiring of the system (normally the ignition switch). Easy thing, but please do make sure to prevent others (or indeed yourself) to accidentially reconnect the battery later on in its old way. Best is to use coloured wires (red for plus) and mark the batteries plus terminal red as well.
Step 2

You reverse polarity of the field (the stator coil in your dynamo housing). Not be changing any wires, but electromagnetically. The field has "to be fired". For this you need a working battery and a piece of wire (about  50-100cm and medium thick)
  • Look first for the wire that comes out of the statorfield and connects to the regulator pin 61. If this does not exist (in DKW e.g.) you have a pin marked DF or 20 or F.
  • Connect the minus terminal of the battery to the frame (make sure the plus terminal is not connected to frame either!)
  • Take the wire and hold it with one end at the plus terminal of the battery and tough it very briefly (just in passing) with the other end and the field connection described above (61,DF,20,F). You will see a few small spark flying. 
And that has been it. The field has been reversed and the system will have from now on negative ground. You may install your electronics.
   

why this field firing? some background
Electricity is generated in a coil (your rotor) that turns inside a magnetic field (your stator). This magnetic field is produced by the current that goes though it (comming initially from the battery). This field leaves important traces of magnetism in the stator, even when voltage is off. Those traces have to be re-orientated towards the new (reverted) flow of current. Otherwise the dynamo will not work. The same has to be done if you install a factory new dynamo that has never been installed (but than, who still has?)