Not been here for a while, far too busy riding me M20 all over the place, BUT, and the reason I'm here. It's got a weird electrical problem, and I'm hoping someone can help...

I start the bike and the Amp meter shows a healthy charge, about 6 miles into the ride the needle drops to '0' and with the lights on shows a discharge, pop into the pub for a pint. And bugger me, the thing shows a charge again, but sure enough after 6 or so miles, it drops to '0' again..?

I'm sure I had this once before on another BSA, but I can't remember what it was, all down to being hard of thinking I suppose...

The bike has a 6v Gel battery and an electronic regulator, I took the battery off and put me tester on it, and it's showing 6.1v...

So it's over to you, thanks for your time..

Had the same problem on my B33 eventually worked out that it was the clutch in the Mag Dyno was slipping. There is a setting for it. I removed the unit and took of the end cover and just tightened the nut a bit on the clutch spider. Solved the problem.

Thanks for the quick reply, I'll have a look see, it's strange cos the needle drops really slowly, when it does start to drop. So perhaps you might have something there..

If you do check the magdyno clutch look at the condition of the flat washer the 'feet' of the clutch spring sit on...

These are very prone to wear/distortion if the clutch has been slipping...(It should be flat)

Most clutches never have the spring changed and many are weak...

I had some thicker washers made which solves the first problem and helps to restore some of the pressure of a worn spring...

If the clutch is slipping you will frequently get an erratic/low voltage output when you test the dynamo output directly....Ian

email (option): ian@wright52.plus.com

The way I read it, everything is OK, it needs some charging after start up, and then the battery is full, when the light are on, it can never charge the battery much, as it goes all directly to the lights, when riding again after stopped awhile it needs charging again, looks normal to me, or am I missing something?

If the magdyno clutch slips it makes a horrible noise, and vibrates too, at least I had that once with someone elses bike.

My 2p.

Lex

email (option): welbike@welbXXX.net (think about this!)

If the battery requires a charge the system will provide it and the ammeter should show a charge without the lights on...The charge rate should reduce to zero as the battery becomes fully charged...

When the lights are turned on it will show a momentary discharge and then the charging system cuts in to balance the load...

The ammeter should then show no charge or a slight charge while the lights are on....

At no point should it show a discharge either with the lights on or without...(apart from the momentary discharge mentioned previously)...

With the lights on if the system shows a moderate discharge it indicates a low system voltage and at some point the battery will go flat...

In any circumstance an indicated heavy discharge points towards a short circuit and/or if the lights are on a total failure of the charging system..

When and under what conditions the regulator cuts in and out to provide or reduce output to balance system loads depends to a degree on the characteristics of the electronic regulator as well as system loads...

Regulator faults can result in unexpected readings at the ammeter...

When checking the system for a fault I usually start at the dynamo, where the power is produced and work on from there...

A short circuit will be self evident with a heavy discharge shown on the ammeter, a flat battery,a blown system fuse, a buggered electronic regulator, melted wires or any of the above in any combination...

Causes of low/no output are a little harder to trace as more parts of the system can potentially be the cause...Ian

email (option): ian@wright52.plus.com

Any electrical problem that occurs after some use, and then disappears after some resting, only to reappear again after some use always points me in the direction of looking for a faulty component not working when warm. Most electrics get a bit warm when used and when malfunctioning they may get warmer. Or the other way around; the malfunction is that they stop working when getting just a little bit warm.
On lots of electronics you can search for problems by spraying freeze-spray onto the components.

I do not know enough specifics about the electrical system on these bikes (currently building my first from a basket case and have not yet come as far as electrics). But say for instance you would hang the regulator out front in the breeze and thereby get a longer riding than 6 miles before failure you'd be on to something. Harder to do that to the magdyno however!

Another question from me is (if I may slightly hijack the thread for a moment): What is the point of the magdyno clutch?

/simon

The drive gear is made from fiber because the armature needs to be electrically insulated from the bike.
A heavy kick back, which is not particularly likely on a soft tuned WM20 this sudden backward rotation can strip a tooth or two from the fiber gear thus the need for a slipping mechanism

Thank you Trevor!

/s

When the armature of my generator self destructed and locked up, the clutch allowed me to still make it home, but the fiber gear was completely worn through when I got back.

email (option): msawicki@mailer.fsu.edu

Sometimes the solder on the collector has molten because an overheated collector. The wires will come loose and when the collector starts spinning the wires move outwards and become detached from the collector thus dropping the charge. DAMHIK Resoldering the connector and finding the reason for the discharge (in my case a faulty battery) turned out to be the solution.

Regards,
Leon

email (option): leonhop3_at_planet_dot_nl