XS650: Permanent Magnet Alternator   Leave a comment

I don’t want to knock the original generating system. It has functioned for the last 40 odd years in one form or another. Designed to be in balance with the machine itself. And it has functioned. Mostly well.

These are Hitachi-no GM here-and have mostly given dependable service. But then 40 years ago I was a teenager. Pumping. Today I’m learning my physical limitations.

It has it’s shortfalls. Don’t you?

If you’ve ever been stranded, using an excited charging system, with a weakened battery or worn brushes you’re going to start thinking the sun has to be shining. Somewhere else. Don’t get me wrong. They are not Lucas. Thankfully. But you’re still stranded.

This topic has been thrashed by now. Over at the Garage, here and here or the Oz site or here.

I remember this discussion starting up some years ago. There is a long thread at the Garage if you want to sort through it. It’s kind of interesting seeing it all develop. Here in Germany this mod has been done for a very long time now. Getting hold of the parts required is not as cheap as it used to be.

This is basically a plug and ride mod. Will take a tech. novice with the parts and basic tools a morning to complete a points bike. A little longer for an electronic ign model.


TCI pickup in the black box 13.00…brushes are isolated…earthed through the rec.reg… if converting to PMA you will lose this and your original electronic ignition


points models have this advance unit on the right hand end of the cam, points to the left


If your bike has a crank-based electronic ignition (TCI) you will need to swap this to a cam-based ignition (points, pamco…). This does introduce some timing errors associated with valve timing. Stretched cam chain, improperly dampening chain adjuster, cam lobe wear, valve wear, malfunctioning ATU etc will all directly affect cam-based ignition timing. But. Don’t worry. The points ignitions on all other XS650s are cam-based and they run just fine.

the complete ATU mechanism..passes through the cam


If swapping from crank (TCI) to cam-based ign you will need to source the ATU-as above-if using points or Pamco. This is the shaft that runs through the hollow cam and the sprung weight mechanism on the rhs. The points or Pamco fit on the lh end. Make sure there are bearings or bushes. A good time to upgrade your coils too.

There are several ways to do this.

  • Source an RD-RZ 250-350 LC/YPVS rotor and stator. ’83 on. (earlier LC-non YPVS have a lower output)


RD350LC/YPVS stator, rotor-not here, backing plate


backing plate dimensions



remove the pickup


you only want these 3 white wires = 3 phase, the rest are not required


  • Pick up a Rectifier-Regulator. An original RD will directly plug and play. New is preferable.


Ascension Cycle Works … pma adapter … ebay


  • Source a Mrriggs adaptor..ebay? Not so sure he is making them any more!! or Ascension Cycle Works … ebay
  • Get a stator only…103 x 42 x 20…mounts directly to the adaptor…endless lists in the links at the beginning
  • Find an RR from pretty much any late model high revving sports bike running a PMA. Some will have 5 wires, some 6, some 7.
  • The colour coding will differ with brand too. If  running without a battery, connect the voltage sensing wire, typically Black on Honda, Orange on Suzuki, and Brown on Yamaha and Kawasaki to the positive output wire. If running a battery connect after the ignition switch so it’s live only when the key is on.
  • Take care if ordering kits … some are only 2 phase … those with 3 white or yellow wires are 3 phase

Just found this  http://www.gofastforless.com/junk/Per-Mag-Alt-Instructions.pdf which deals with the topic fine.

electrolytic capacitor…use the one with screw posts…25V 10000uF


You can run this batteryless using a capacitor…25V and 10K uF. I’ve done this for quite some time now with no problem, however I get a little nervous sometimes wrt reliability. I am about to add in a small gel battery. If my alternator stops charging my Pamco requires so little current I will still get home.

small gel battery


fitted, wiring laid


easily wired in…with or without battery


83-85 RD-RZ basic data … later 86/87 have VCD-88/ND AC Generators with 13A output@5000rpm


As I say, apart from a slight risk running batteryless I like this. After adding a battery I will feel good.

It’s a bit lighter, allowing slightly freer revving. For track purposes however a total loss system makes things even easier.

One more point here. These girls are starting to show their age a little, mostly gracefully. Personally I distrust the complete electrical system and usually take this chance to rip the lot out. I then fabricate my own simplified wiring. Doesn’t take long, reduces weight, makes space and you know what you’ve got.



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