Odd charging problems on '75 xs650

[Niels558]

Hi members,

trying to help out my friend on his motorcycle with probably a minor electrical issue, I am walking in to a problem
I cannot figure out. Really hoping to find a answer from someone with specific experience working on these bikes!

We started off with a bike that wasn't charging, but running just fine. Drove for quite a bit with it, but after an hour or so we saw lights dimming
and didn't want to go on.
Putting the bike in and hooking up the multimeter we found the voltage dropping way down as soon as we switched it on (no running engine);
there must be a leak somewhere. We found this leak to be in the rotor, after taking the rotor out we saw the voltage staying stable when we switched
the bike on (still no running engine). Ordering one took a while, but it finally arived after some weeks.

After putting in the new rotor, we still saw no drop in voltage when we switched on; nice! But then.. we started up.
Voltage went way up, to 20+V on the battery poles. That must be a broken regulator I thought, and took the manuel for the resistance
it needed to have: it was all spot on. (I was burning trough main fuses at this time, cause letting it run for longer than a few seconds to take
a measurement was already too long for the fuse to survive) I did already screwed down the regulator to a minimum outgoing voltage in the end without result.

I cannot think of a different component that can cause this problem, but I'm hoping to find an answer in this experiencebox online here!

Thanks in advance en kind regards,

Niels

 

[jetmechmarty]

Tell is about the motorcycle. What year model is it? Is it Euro spec or a US import? Does it have a mechanical or solid state regulator?

 

[Its been a long time]

99% certain it's the regulator. If the rectifier is as old as the bike, I'd change that too as well as the regulator. I am doing the change next week on my 77 650 which should essentially be the same.

 

[Its been a long time]

Tell is about the motorcycle. What year model is it? Is it Euro spec or a US import? Does it have a mechanical or solid state regulator?

'75 XS650 in the thread title?

 

[Niels558]

Im sorry for not putting the year in the text, it is a '75. It is a original Dutch motorcycle with a mechanical regulator from way before my time (I didn't know these things existed!) This apparently means that the regulator and the rectifier (correct me if im wrong, i use googletranslate for these terms) are to different parts instead the one thing I am used to from my other bikes (all a bit younger).

 

[Niels558]

99% certain it's the regulator. If the rectifier is as old as the bike, I'd change that too as well as the regulator. I am doing the change next week on my 77 650 which should essentially be the same.

That was what i was thinking, but they are not cheap. I have no problems buying new stuff if needed, but i was confused cause of the good results while testing the regulator by the workshopmanual...

 

[jetmechmarty]

https://www.xs650.com/threads/diy-reg-rec-5twins-and-jim.55842/

Hopefully, this reference will assist you.

 

[Melnic]

Post 84,
sure you adjusted the regulator in the correct direction?
I believe its CCW to lower voltage (reduce spring tension to let the coil move to the higher resistance sooner)
https://www.xs650.com/threads/1978-xs650-special-project.65053/page-5

Im also wondering if your rotor is really the right coil resistance if its putting out 20V at idle.

BTW, I get a battery voltage drop of about .3V-.4V (drops from 12.7 down to 12.3 to 12.4 )on my bike when I turn on the switch just from a load of the lights and rotor. What kind of battery do you have?
new Battery?

 

[Its been a long time]

Im sorry for not putting the year in the text, it is a '75. It is a original Dutch motorcycle with a mechanical regulator from way before my time (I didn't know these things existed!) This apparently means that the regulator and the rectifier (correct me if im wrong, i use googletranslate for these terms) are to different parts instead the one thing I am used to from my other bikes (all a bit younger).

Yes, you will find the rectifier under the battery tray. Three white wires from the alternator to the rectifier.

I bought a new (Chinese) rectifier and a generic voltage regulator from eBay (I think for Peugeot and Lada typically). Just need to finish off making some new wiring, then I'll fit them next week. Rectifier was about Euros 5, regulator about Euros 15. Plus the plugs and some coloured wiring. Say around Euros 35 for everything.

Did you check the new rotor winding resistance to be sure it's in specification? Best to check.