View Full Version : xs650 PMA no charge

07-13-2017, 4:55 PM
1978 xs650, randomly stopped charging. I run the Hughs handbuilt pma and have for 4 years with no issues. Open loop on regulator so I replaced, no charge still and I'm getting postice voltage between the negative on the battery and regulator ground. Stator tested okay, .4-5 on two of the 3 terminals, .9 on the other, Hugh seemed to think maybe the stator was on its way out, ok, replaced that too. Still getting voltage at the ground and not charging. Hugh said replace your key switch Seen those do weird things, ok did that no change. Even though I know for a fact my battery is good ran the charging system independtly to a brand new out of the box battery no change. Have the wiring harness apart, no chafs no broken wires all grounds are good bike fires right up first kick runs and rides perfect until the battery gets low. With load all lights and ignition it's not dropping fast and battery stayed at 12.8 for a couple days off the charger not riding the bike. I'm stumped. Hugh is stumped. I've thrown hundreds of dollars at it now and still won't charge, anyone have any idea why this is happening?


07-14-2017, 6:48 AM
No experience with the PMA...
What AC amperage and/or voltage does Hugh expect and what are you getting straight off the alt?
Maybe the magnets are weak?

Should be a static and dynamic test for the reg/rect too

07-14-2017, 8:27 AM
I've read you're supposed to see about 15-20 at idle and high as 40 to 60 between 3k and 5k rpm, but that was the old stator, I've since replaced with a brand new one and have no change. Regulator and stator are both brand new. Last night the last thing I did was start tearing things off one by one and testing voltage between my negative terminal and ground on other things and I narrowed it down to the ignition, my pamco is back feeding 18v to ground which I don't understand at all because I had the charging system completely disconnected and the battery was only at 12.6 so how can an ignition generate voltage higher than battery voltage without blowing a fuse or melting the ignition. And why if it's sending power to ground is it making the charging system not work. Currently I have no ground strap for the battery to frame ground. I have the regulator hooked directly to both terminals on the battery and I was seeing slight slight change in rpm revving it but it wouldn't go over 13 volts. Again stator and regulator are both brand new out of the box.

07-15-2017, 6:37 AM
New doesn't always mean good
Did you check voltage and amperage?
Is voltage out the regulator rectified? DC
What kind of batt? Size?
Wire gauge?
Why ditch the frame ground? Regulators need a big shunt.
Better to wire ignition/coil(s) direct, ditching the suspect ignition switch

07-15-2017, 2:04 PM
Sketch your exact wiring schematic for the ignition clearly and post a pic.

Do the same for the charging system. I know there isn't much there, but do it anyway.

Note exactly everywhere you are checking for voltage and where the supposed "backfeed" (unexplained voltage disparity really) is measured.

07-15-2017, 3:01 PM
maybe the new stator was bad.

07-20-2017, 8:51 PM
Coming back to this now sorry guys. Updates. I went through the harness and made a new ground strap for the battery to frame ground, which got rid of my ignition to ground positive voltage but now killed my spark somehow or that's completely coincidental. I was already waiting for an ignition from Hugh in the mail, got that wired it in still nothing. Tonight I wired the ignition and coil to a battery on the floor, and pulled the pin on the advance rod so I could spark by hand. No spark. I had a new unopened coil and new wires and caps in a box, I took those out wired it up, still no spark, everything is seperate from the bike. Full battery voltage at coil, .7 drop at the plate but has 12 volts continuity checks out on everything ignition related. So forget the charging issue I'm completely stumped. Hugh has no idea why it won't charge, Mikes xs has no idea why it won't charge, PamcoPete has been shoddy at best at answering emails, any xs650 person has no idea and no one else that has no trouble building motorcycles from scratch can give me any idea as to what th fuck is going on. At this point I'm either going to order everything brand new and completely re wire the bike or just light it on fire. As it is right now every electrical compeneant in the charging system and ignition sans the e advance is brand new. So what I gotta double spend money here and order everything again? I vote fire. Paper weight of a bike missing all the summer riding with my friends after I was done first and riding for two months solo with absolutely zero issues and now I'm having catstophic failure of everything.

07-23-2017, 5:29 PM
Maybe you've already tried but keep it as simple as possible. Unhook everything and wire the Pamco alone to a fully charged battery with a toggle switch wired in between. If you don't get spark then you'll know the ignition is bad or the coil is bad. If you do get spark and it fires, then start adding back in lights etc. If all goes well then add in the PMA last. Sounds like you have but triple check all grounds. Do you have any soldered joints in your wiring that could have failed?

07-25-2017, 5:52 AM
THIS is but one of the many reasons I opted to use the
POWER DYNAMO setup from Hoos racing.
You have as much in your PMA as you would into a much better unit from Hoos.