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Old 08-08-2012, 09:23 AM   #1
jconly OP
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Joined: Aug 2009
Location: NYC
Oddometer: 434
On the road - inconsistent voltage, help diagnosing please!

The bike should be sitting around 14 --> 14.3 V at all times while running, correct? And what is the resistance range for the coils of the generator. Manual says 1 OHM max, but what is the min value?

And the full story:

So, turns out I'm getting some REALLY erratic charging behavior, and I'm suspecting this is not normal.
This is the first ride I've done with a voltmeter mounted, but it just doesn't seem right.

Currently at a friends garage for a few days, and have begun doing some testing with the multimeter, but have some questions for you on specs, where the manual fails to give the info.

First off, a diagnosis. It all started when I probably made a major mess up and accidentally shorted the two wires on the starter relay pre-trip. During the ride, my voltage was all over the place, but basically it breaks down like this:

With the battery at a full charge, IE: 12.7 V, and I key on, voltage comes down to about 12.2 V.
I start her up, and it comes to around 13V.
If I let it idle, with only the low beam and my GPS and voltmeter powered on, it will OCCASIONALLY come to 14V, and sit there.
Any application of throttle drops my voltage down to anywhere between 13.1 V --> 13.4 V. If I roll off the throttle, it will occasionally climb back to 14V but will NEVER see more.
If the fan comes on at idle, voltage immediately drops down to 12.7 V.

Being on the road, I haven't had the heart to let it sit like this and see if the voltage continues to drop as the battery drains. I've always either turned the bike off to cool, or taken off down the road to push the voltage back to the 13.1-->13.4 range.

So first things first, I needed to confirm my findings with an accurate meter.
Yep, at 5000 RPM's, the reading at battery is only 13.35V, not the 14-15 the manual states it should.
All connections looked good, so on to the generator.

None of the three coils are grounded to the engine case, so that's good.
Next the resistance test.. well here's my main question for you:

What is the lowest acceptable resistance one should find between generator coils?

I've been following this flowchart found HERE, keeping in mind its generic, and cross-referencing every figure with what I could find in the manual. Interestingly enough, the manual only states a max resistance of 1 OHM, whereas the generic chart states a grange of .5 --> 2 OHMs.
All of my coils are returning a value of .2 --> .3 OHM. Is this normal?
Other than this, the generator passes the AC output test, with all 3 readings across coils outputting around 62 VAC. (Based off of the chart, stating I should be looking for even #'s > 50 VAC. No actual figure for this in the manual that I could find.)

I'm about to move onto the RR now, and do some tests on the diodes, but before I do, I wanted to make sure that my generator is in fact still good. Seems that way, but just wanted to confirm my resistance was in spec.

Right now, it's looking more and more like I toasted the RR when I crossed those two wires (twice actually.)
Does this seem possible?
One last question for you gurus... are my voltage figures accurate at 13.1 - 13.4 V while riding, or should this baby be putting out a solid 14 --> 14.3 V at all times, like every other bike I've owned?

Thanks!!!! Your prompt help is so greatly appreciated! Hopefully this little issue will help teach some others about our charging systems as well, since I couldn't find any solid figures via search.
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