Powerdynamo, use of regulator R81 in various 6V dynamo systems

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Regulator 80 50 588 03 
we get asked nearly every day whether this regulator may be used in a motorcycle XYZ. To save us from repeating answers we detail the needed information here:

The short answer is:
this regulator may be used in all 6V dynamo systems with negative ground (important, battery minus has to be to ground) and a power of max 100W, having at least 4 field coils and a field resistance of at least 2.5 Ohm. It may be used in ambient temperatures of between -20 to +80 C.
But, in order to get it working you will need to take the stock regulating resistor out (resp. deactivate it by cutting connection to it) - and exactly here is the crux of the problem.


Every 6V dynamo has a regulating resistor to feed the field with a minimum current. Without this no stock dynamo would work. For the electronic replacement however this resistor is poison. The regulator will not work when the resistor is present.

It has to be taken out or electrically disconnected.

As stated above, this brings the real problem as this resistor is in many cases hidden from sight.

Also, there are 2 alternatives of how this resistor is originally connected. One side of it is always to the field, the other may be at the plus carbon or the minus carbon. For this reason our regulator has 2 pins for the field (DF)


  • in some, unfortunately only a few systems the resistor is a descrete, highly visible part, so in MZ 65W and BMW 2valve boxer. Here disconnecting the regulator is easy.
  • in some systems the resistor is inside the stock regulator and automatically gets eliminated when this is taken out. Super simple - as long as you know which systems are like this!r
  • in very many systems the resistor is a short piece of special wire which has been added to the field coils and is therefore not really easy to detect.
    As long as there are only 3 wires exiting the dynamo it is plain, 2 have to be the field, the 3rd runs to the resistor. In many cases however you are faced with more than 3 wires exiting.

To bombard us with questions of how to find this resistor in some XYZ installation does really not make any sense. All we know has been put into the  instructions for this regulator. More we simply do not know. There have been so many versions. We have already spent endless hours on this part and we are not willing to add more time. We will however gladly add customer information to our instructions which surely would help other customers.

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