Charging issues

[dankeller]

Thank you again Guy. I truly am indebted to you for all your help and valuable information you post on this board.

I will keep you posted.  Its been raining today so I can't test whether the new stator fixed my charging issue.

I did check, and can confirm that with the key on (motor not running), I can turn the headlight on with the handlebar switch (high and low beam).   The rear red light also comes on.  This is how it worked before.  My headlight never turned on automatically.  So I am still puzzled as to how the relay is intended to work.  Maybe on mine, the relay has alway been stuck in the on position (which would make me lucky), so I never noticed.

I can't wait to run the bike, and I'll report back with my findings as soon as I do.

Many thanks.

Dan

[dankeller]

Just tried it in the driveway.  At 2000 rpm headlight off I get 14.3 volts. Headlight on I get 13.3volts. At 1300rpm headlight off I get 12.65 volts. Headlight on about 12.15volts.

The idle volts with headlight on seem low.  I encounter a lot of stop and go traffic on my route to work so this worries me, if this is normal. But I'd like confirmation that this is normal so I can let it go. Another member said they got 13v at idle with headlight on. But I have the newtronics ignition so maybe that takes additional voltage.

I still have to see what happens to the charging when the bike is hot.

Dan

[dankeller]

Drove around today and am getting good voltage numbers.

To summarize, i was experiencing poor charging volts on my 78 xs500 when the engine was at operating temperature. I did some tests (see Guylr's very helpful posts on this) to try to find what was causing the problem but found nothing definitive.  I felt I ruled out problems with the voltage regulator and rectifier, the field coil, and wire connections.  I had no shorts to ground. I decided to replace the stator because it has been the reason for poor or no charging in several other cases.

I replaced my stator with a NOS one purchased from eBay.  It was described as being for 73-77. The new stator was different from mine in that it was missing a fourth wire, for connecting to the harness to a relay. It turned out that it didn't make a difference and I left the single plug on the harness disconnected.

At idle (1200-1300rpm) with headlight on I get a voltage of 12.15 volts, with headlight off about 12.6v. At 2000 rpm headlight on 13.3v and off 14.3v.  When riding, at 5000 rpm with the headlight on 14.88v, headlight off it drops to 14.6v.  I haven't experienced the heat related decrease in voltage I was seeing before.

I would appreciate it if someone can confirm the idle voltage both with and without lights on.

As an aside, I also experimented with the ElectroSport ESR352 combination regulator/rectifier.  They claim it is plug and play, but it is not.  It will blow your main fuse in its original wiring configuration.  To make it work I had to swap the red and black wires on the rectifier side, and the brown and green wire on the regulator side (this matches the wire colours on the harness connectors for the rectifier and regulator).  I also had to pull out the brown wire female terminal from the plug coming from the field coil, and connect it to the negative terminal on the battery (I used a short wire with alligator clips at both ends).  It seemed to give lower voltage at rev.  I went back to using my original voltage regulator and rectifier since it works and they are hidden.

If any one else here has a running xs500 I would appreciate it if you could measure your idle voltage with lights on and off, to confirm what I am seeing. Thanks.

Dan

[johanjk]

Hi!
I have the same problem. I have an electronic ignition.
Have you found a way to solve the problem?

Thank you

[guylr]

Dan's charging voltages from his 2016 post were right on and normal. The bikes don't charge enough at idle with the lights on to keep the battery up. You will see the charge voltage break even and go above 12.7V at about 1,700 rpm and if you see more than 13v above that with the lights on you are good.

Guy