Not Charging

[Gpaws1968]

Good morning all,

I need help with this one. My 1981 XS 650 is changing what it looks like, 8 volts or so. I thought it was the regulator, so I replaced it, and it's still the same. I then removed the stator and tested it, 0.8 ohms between the 3 white wires, no short to ground. I checked the rotor, and I'm getting around 5 ohms between the slip rings and no short to ground. I did notice that the brushes are different lengths, but they seem to be making contact.

When running, it charges at around 9 volts

 

[5twins]

The spring looks like it's been changed on that "short" brush? I'd replace that one. And I prefer to use original brushes, not re-pops. They can be found on eBay for about the same price as the aftermarket ones.

 

[gggGary]

I would have put in new brushes as a first step if doing a "scattergun" approach to charging issues.
Worn brushes is the "most common" charging issue. Those "look" long enough but why is one barely sticking through the holder?
Your other tests seem good, good pics!
8 volt, 9 volt is not "charging" at all, and is pretty pathetic for a fully charged battery in a bike that's just been started.
does the headlight light?
bike running check voltage across the brush tops, what do you get?
Remove, check the ground strap from battery to frame.

 

[Its been a long time]

In the first picture, one of those brushes isn't orientated correctly. The brushes look long enough, but otherwise they don't look great. I'd fit new brushes, making sure both of them were orientated correctly. Then see how it goes. Whilst doing that, I'd double check grounds for cleanliness and a good electrical path back to the battery.

 

[gggGary]

a good charged battery should keep the bike at 11 volts or so for at least a few minutes when first started.
Has the battery been tested?

 

[gggGary]

The spring looks like it's been changed on that "short" brush? I'd replace that one. And I prefer to use original brushes, not re-pops. They can be found on eBay for about the same price as the aftermarket ones.

Yes that solder blob on top of one brush isn't right. Get new brushes before proceeding. Good chance that's why the PO sold the bike?

 

[Gpaws1968]

The spring looks like it's been changed on that "short" brush? I'd replace that one. And I prefer to use original brushes, not re-pops. They can be found on eBay for about the same price as the aftermarket ones.

The wire and the spring is shorter

 

[Melnic]

a good charged battery should keep the bike at 11 volts or so for at least a few minutes when first started.
Has the battery been tested?

When I got my XS650 running and discovered it was not charging from a burnt rotor, the bike was idling and battery was at 12.3V.
This was a brand new battery that I charged up with a charger.
12.6V before starting and 12.3V while idling with the burn rotor.
If his battery is below 11V your spot on for suspecting Battery IMO.
Since my battery was @ 12.3 w/ a burnt rotor, that means the rotor was basically open circuit.
I think he could Disconnect regulator and see what happens. If the voltage goes up and its idling, then regulator may be at fault.

Again, voltage is measured at battery terminals.

I highly suggest moving to a VR115 regulator (search it on this site). (EDIT: See Jim's correction below

 

[Jim]

I highly suggest moving to a VR115 regulator (search it on this site).

The '81 doesn't use the VR115. You'll need a VR794 or equivalent.

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