14.5 V without headlight fuse.

[fenianmoto]

Hi, I'm new to the forum, longtime rider & wrencher, mostly Honda fours & brit twins.

So I've been working on a friends newly aquired XS, it's a 1980 w/ CDI. She's having charging problems, so I started digging around, testing, & researching. Going by the shop manual's method for this bike, it mentions pulling the headlight fuse for the test. I did that, and it's getting a good 14.5 - 14.8 volts above 2000 rpm's. With the fuse in, it struggles to hit low 13's at that same point. I looked at Curly's charging test on this forum as well, and when I cleaned & then measured the slip rings on the rotor, they measured just over 2.

The brushes are new, every contact has been cleaned, grounds checked etc. Ordered a new rotor, but I'm still wondering why the initial system check with the fuse pulled seemed good. Any other feedback would be appreciated. Thanks!!!

 

[pamcopete]

fen...,

If you mean that you measured 2 Ohms across the slip rings, then the rotor is toast.

Go here for a rebuilt:

Custom Rewind
2014 Pratt Hwy.
Birmingham, AL
35214

Call Gary first. Great guy.

800 798 7282

Measure again to be sure with the brushes removed. You will also need a rotor puller. Don't try to remove the rotor without the puller. Custom Rewind sometimes has a puller they will loan you. Other wise, www.mikesxs.com Be sure to remove the nut on the end of the crankshaft before attempting to remove the rotor. No joke. Some have tried.

 

[fenianmoto]

Thanks Pete! I measured the rotor with the stator removed, cleaned it & still had low ohms. I ordered a puller with the new rotor.

Does the 14.5 volts with the headlight fuse removed make sense? Would that have anything to do with the safety relay for the headlight I wonder?

 

[pamcopete]

fen....,

The headlight is the largest load on the alternator. When it is off, even with a bad rotor, you can get 14.5 Volts, so that indicates that your stator and reg / rectifier is OK and it's only the rotor.

Did you go to Custom Rewind for the rotor?

 

[fenianmoto]

That makes sense to me, and the other components in the charging system did indeed test ok. I wasn't sure about the extra relay, & how that comes into play.

Ordered the part from a shop in Ohio, I'm in Chicago, & we needed to be able to get it here within a couple days. Road America vintage weekend & racing is next weekend in Wisconsin

Thanks for the quick reply Pete!

**Forgot to mention, the rotor's the one made by Electrosport, should be ok, I've had good luck with their Honda replacement parts over the years.