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xs650 > > Frank-in-Bike, Non XS parts that are Interchangeable > > Electrical and Lighting > > Weak Charging - Open to Suggestions


Weak Charging - Open to Suggestions
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acbanks
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Joined: Mar 21, 2009
Posts: 72
Location: Raleigh, NC, USA

PostPosted: June 21, 2009, 8:35 pm    Post subject: Weak Charging - Open to Suggestions

Hey guys, I have a 75 model that's just not charging as well as it should. It struggles to hold it above 12 volts at idle and only manages 13.2 at 2000rpm(dropping past that point due to the extra load from the coil).

I've gone through the entire harness cleaning the connections. I've replaced the original key and kill switches with new. I've cleaned the rotor contacts and replaced the brushes(I'm showing a .3 volt drop from the battery to the rotor). The mechanical voltage regulator is in the closed position. I've replaced the rectifier with the Radio Shack fix.

Resistance of the rotor windings and stator windings all check what they should be according to that guide over on the proboards site.

Between the white wires coming from the stator I have a consistent 10VAC on each(at idle).

I'm running the stock headlight and a single taillight.

What should I do next? Thanks.
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pamcopete
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Joined: Oct 10, 2008
Posts: 875
Location: South Carolina

PostPosted: June 21, 2009, 8:57 pm    Post subject: Re: Weak Charging - Open to Suggestions

acbanks,

The coil load does not increase with increased RPM. The points are closed for 93 degrees, or 186 degrees cam shaft total for both, so the duty cycle is 50% regardless of the RPM.

When you check the battery voltage with an electric start, you should wait a couple of minutes for the battery to recovewr from the start before checking the voltage.

The contacts on the regulator may be closed when at idle, but they will open and close rapidly to regulate the current to the rotor winding. They have a tendancy to regulate poorly as they get older and yours is 33 years old. Time to replace it with a solid state regulator.

If you install the chrysler Regulator, it does require you to isolate the grounded brush and apply +12 to it, but it is less than $15 and comes with a one year warranty.

The VR291 option does not require any modification to the brushes, but it costs about $28.

The test for this is to unplug your regulator and apply battery through a fuse directly to the green wire brush. Rev the engine up to 2500 RPM and check the battery voltage. Do not let the voltage go above 15 Volts.

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acbanks
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Joined: Mar 21, 2009
Posts: 72
Location: Raleigh, NC, USA

PostPosted: June 21, 2009, 9:09 pm    Post subject: Re: Weak Charging - Open to Suggestions

I've jumpered a 12v wire directly to the rotor with no improvement in charging(I've also physically held the regulator points closed, but I haven't seen them open anyway.)

The only electrical contacts I haven't cleaned are the ones at the stator, but I assume I would have to pull the rotor to get to them.
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acbanks
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PostPosted: June 21, 2009, 9:20 pm    Post subject: Re: Weak Charging - Open to Suggestions

Just realized that I'm the wrong section...this bike is stock.
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pamcopete
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PostPosted: June 21, 2009, 9:24 pm    Post subject: Re: Weak Charging - Open to Suggestions

acbanks

The contacts for the stator are in a connector behind the lower part of the engine where the wires exit the stator. You don't have to remove the rotor to get to the connector.

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acbanks
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Location: Raleigh, NC, USA

PostPosted: June 24, 2009, 10:41 am    Post subject: Re: Weak Charging - Open to Suggestions

After cleaning every connection in the wiring harness(again) with a nail file and sanding the rotor contacts with 600 grit sandpaper, I've got a steady 12.5V at idle, up to 13.4 at 3000rpm. After that rpm it still falls like a rock. After watching the voltage regulator, it looks like the high-rpm vibration literally shakes the regulator points open. I might could clean the points and adjust it tighter, but I think it's time to buy a Chrysler electronic regulator.

I just realized that you posted the plans for the rectifier replacement as well. It's working great, but man that sucker gets hot. Even with a fat computer heat sink it's hot enough to burn you. Anyway, thanks for all of your help!
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pamcopete
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PostPosted: June 24, 2009, 11:34 am    Post subject: Re: Weak Charging - Open to Suggestions

acbanks,

Well, the rectifiers do get hot, that's why they are mounted on a heat sink, but probably not as hot as you describe them. It wouldn't hurt to un plug the rectifier and check the diodes. Typically, if one of the diodes in the rectifier shorts out, you will still get a usable output from the others. The shorted diode will cause the rectifier to overheat, of course.

Remember that you have a spare diode set available if there is a shorted diode. Just move the white wire from the shorted diode connecition over to the spare connection.

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acbanks
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Joined: Mar 21, 2009
Posts: 72
Location: Raleigh, NC, USA

PostPosted: June 24, 2009, 12:49 pm    Post subject: Re: Weak Charging - Open to Suggestions

Rectifier diodes all check good.(Flow only one way between whites and red and whites and black, respectively.)

After the cleaning I again jumpered 12v directly to the rotor. Voltage at 3000rpm was 16V and climbing.

I cleaned the voltage regulator points with fine sandpaper and adjusted the set screw to tighten the spring a bit. This was enough to hold the points closed despite the shaking yet still open them at 14.6V.

So that's a complete success. I'll probably still order an electronic regulator soon(and when budget allows, electronic ignition!)
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pamcopete
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PostPosted: June 24, 2009, 12:58 pm    Post subject: Re: Weak Charging - Open to Suggestions

acbanks,

OK. I was basing my reccomendation on your earlier report that the voltage did not get to 14.5 even when you bypassed the regulator.

As for adjusting the crude, mechanical regulator, be aware that the voltage may change upwardly when you replace the cover on the regulator after adjusting it and that it does a poor job of regulating when the revs get up to 5,000 RPM and the alternator is producing a higher voltage, requiring the regulator to reduce the rotor current to a low value.

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1980xsRider
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Joined: Aug 13, 2009
Posts: 22
Location: Colorado

PostPosted: August 18, 2009, 4:34 pm    Post subject: Re: Weak Charging - Open to Suggestions

I know they went to a different ignition/charging system in 79 or 80. Does the above issue occur often in the 1980 and newer bikes. Did the transistorized ignition help with the type of problem that acbanks described above.
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