(translated by Andreas Kraft Okt.2003 and English Brian)

Problems with the AC generator, or when the light begins to fade.

Report No 1 by Erik Hasenäcker ( March 2000 )


Last Sunday I took the bike out for a ride, the weather conditions were perfect. The air must have been very dense and the Oxygen content high, as my bike almost reached Warp Factor 9.9!

After riding for a while the headlight beam began to grow dimmer. I drove back home and straight into the garage. At first I measured the open circuit voltage, it should be around 10 to 15 Volts, but I measured 4. I removed the right-hand side cover (drive-side) and the generator coil (note the cable size used for the "generator coil ". A minimum of 1.25mm2 is recommended for higher current).

This happened to me before 6 months ago and it was solved by fitting a second-hand generator coil. I stripped the windings off of the old coil and got a total of 13 metres of wire. In the lower layers of the coil I observed some cracks in the insulation, together with some minor oil residue (don’t ask where that is coming from) a short-circuit was inescapable.

However, the decision was clear:
Only a new generator coil would help. An investigation on the the original microfiches revealed that the generator coil was no longer available.

I went to a professional electric coil winder and bought all the necessary parts. The wire now is double insulated. I wound the coil by myself (which is a f***** hard job for the fingers). I took the coil back to the professional for re-sealing. This is done by encapsulating in resin and baking.

After re-assembling the generator, I tested the coil by revving the motor to about 7000rpm. The light was shining like hell/a supernova (whatever you prefer) and the lamps were still working. I haven’t measured the output voltages, but it seemed to be OK 'cause the lamps are still working.

Now we have to test the length of time, I am confident. If it is too short we have to cut the wire.



Report No 2 by Stephan Oettle

Dear Volker,

I’ve repaired the dynamo. Erik has a XL500 S with 6 Volt. The 12 Volt dynamo looks different: I replaced the existing wire (length 9.5m, diameter .8mm) by a wire with a diameter of 1mm. Now the light is shining bright. A regulator terminates the overvoltage, the electric coil was sealed by 5min epoxy resin.


If you need more information concerning the repair of the dynamo, just contact me.

See you, Stephan

Report No 3 by Erik Hasenäcker ( August 2000 )

Hello Volker,

The thickness of the wire should be 1.25mm, please correct. By mistake I wound a generator coil with 1.8 mm wire, now it is a "Power-coil". No problem with that, you only have to change the front lamp to a Billux 6V45/40Watt. But then you have such a bright light. Take care that you use a shorter wire. I stick to it. I made a 40 km test drive today, full speed, everything OK.