I barely get over 13V above 3500 rpm and higher. My regulator is stock mechanical, but does not have the adjustment screws to vary the output. Battery is one year old, will hold a full charge overnight. My rotor slip rings are clean, resistance between the rings is 6.5 "hot"(after a 5 mile ride), resistance between the rings and ground is infinity, and my brushes appear to be in good shape. I have about .1-.2 volt drop through the ignition switch, measured at the brush. That seems to be reasonable based on my research here on the forum. However, the "slap test" is negative- no pull down at all. Given that, I'm inclined to get the rotor rewound before I start fooling with a new regulator or any other mods. I've cleaned every contact I can think of. If the rotor is "sound" and I have 12+ volts at the brush, I should get a good slap test, no?
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Poor battery charging, next steps?
- Thread starter Pat D
- Start date
I'd first suspect the regulator. If you have 12VDC on the green brush wire screw, then check to see if there is continuity on the black wire brush screw to ground (battery negative terminal)
You could make up a jumper wire and jump from the battery 12v pos to the positive brush on the stator. That will bypass the regulator and you should get good magnetism.
All the regulators have adjustments. You wouldn't be the first to be looking at a safety relay and not at the regulator.
The regulator has the big green cylinder below it. (the ballast resister)
Check you are getting +12 on the lower brush.
PS 40 years on parts mixing and "matching" is common, your brushes should look like my pic above and NOT like these.
Oof. It's hard for me to tell, but it looks like the regulator in your pic with the big green ballast resistor is mounted on the left side of the bike. That is where what I thought is my regulator is also mounted. See pic. However, my manual shows the regulator mounted on the right side of the bike. The unit from the left side of my bike, with what appears to be a ballast resistor (but not green), does not have any adjustment screws. See pic. The unit from the right side of my bike does not have the resistor. Last pic. Let's make sure I know what I'm looking at.
Thanks for great detailed pics! you can do a rectifier check also.
Yeah the one with the "black painted" resistor. Doesn't look like any of the stock regulators?
Is that screw near the base an adjustment screw?
Yes, that's the regulator. Not all regulators have adjustment screws. For instance, the RD350 used one that looks just like yours... needed to be bent to adjust it. I suppose it's possible yours has been swapped with one not made for the XS. 
Jim's rectifier yootoob link https://www.xs650.com/threads/engine-heating-up-and-shutting-down.64361/page-4#post-810675
No, it just holds the assembly together and makes a connection- it's well insulated from the regulator chassis.
Could be- it really doesn't lend itself to bending with any degree of precision, short arm and stout material. This is irritating as I've been dealing with, setting and adjusting mechanical VR's in automotive applications for over 50 years, 6v, 12v, generators, alternators. This bike has proven to be most challenging from a charging perspective ...Yes, that's the regulator. Not all regulators have adjustment screws. For instance, the RD350 used one that looks just like yours... needed to be bent to adjust it. I suppose it's possible yours has been swapped with one not made for the XS.
Yep, just verified.
A "correct" XS650 regulator is adjustable, like you are used to doing.
I have extras that need a new home.
I have extras that need a new home.
If it were me, I think I'd go ahead and swap that regulator out for a newer solid state one. At least that would rule it out as a culprit... and give a better charging system.
What year is your bike?
