D/S XR650R Charging Problem...

In the process of Dual-Sporting an '02 XR650R. I installed a regulator/rectifier purchased from Ricky Stator, first wiring it into the stock wiring lighting coil. I also plugged in a new 12 volt sealed battery. When I fired it up, I found that voltage would rise with the engine RPM, but would just break 12.5 volts, not enought to keep the battery charged. I have since re-wound the lighting coil, wrapping all 10 poles with 18 gauge copper magnet wire. This has increased the voltage output, but it still just touches 13 volts at high RPM, even though I'm still using a 35 watt headlight and standard tailight (nothing else is drawing off the system). I still fear that the battery will go flat, plus I was hoping to use a higher wattage headlight. Any ideas as to why I'm getting such a low output?? Thanks in advance!

What is the voltage across the battery terminals? If the battery was not properly charged from the get go, this may be part of the problem. I know that most sealed batteries claim that they are ready to go right out of the box, but this is not always the case. If they have sat on the back of a shelf for a long amount of time, they may not be as "fresh" as they could be.

What is the voltage of the system just off of idle (at say 2000 rpm)? It may be that the system is operating properly, you just happen to actually be charging a battery as you are testing the wires with the multimeter. If the voltage is really low at this point, then you definitely have a wiring issue. Throw a higher wattage bulb in the headlight. If it doesn't get dim when the bike is idling, you are probabaly ok.

I also have a rewound stator on my bike. If the battery is run right down I will still have over 12 volts alittle above idle while it's charging(14volts). It would also charge the battery with the stock stator just not at idle. How big is this battery? With a rewond stator you should have enough to charge the battery and still have 12+ volts above idle. I'm not really helping I know. What's the voltage befor the regulator?

I'm actually having the same problem using a White Bros Battery Eliminator (basically a big capacitor). There is a voltage difference across the terminals, but it has yet to charge noticeably, if at all. This is with a rewound stator as well.

No constructive input as yet, but I'll keep you updated.

First off, thanks for the feedback thus far. This is the second XR650R that I've "dual-sported". First one used the stock lighting coil and is charging the battery fine. This lastest one is driving me nuts. The battery in use is a new, sealed 1.4 amp/hr unit that I fully charged prior to use. I first wired everything up with the stock lighting coil, tail light and 35 watt headlight, but it only produced around 12.6 volts at high rpm, dipping to around 12 volts at idle. Based on this, I decided to re-wind the coil, doing so using 18 gauge wire on all poles, resulting in approx 330 wraps (as per prior intructions found in this site). This resulted in a slightly higher output, closer to 13 volts at high rpm, but never into the 14 volt range where I'd like to see it. I got ahold of my first XR650 project for comparison. It produces close to 14 volts at the battery even near idle (with the stock coil). I even swapped the reg/rectifier unit between the bikes, which didn't change the output at all. I also compared the AC voltage output at the wires just prior to the reg/rectifer. My meter showed 8.5 volts on my latest project, and up around 12.5 volts on my original project. I double checked my rewound coil, finding that it's resistance was .6 ohms, right were it should be (?). I'm still thinking that the coil is the problem, but whay didn't the problem change much even when I re-wound the entire thing (yes I alternated the windings). Like I said, It's driving me nuts. Thanks again.

If you happen to have the stator cover off have a look at the directions of the windings. If you went the wrong way on the first winding(easy to do) it will still function but the first winding's power will be subtracted from the rest. The overall power would be higher then that of the stock coil but not by much. Just something to look into. If all else fails could you swap them between the 2 bikes?

As to the re-windings, I removed all of the stock lighting coil windings from the 4 poles that they covered. I then rewound these poles and the rest, 10 total, with the 18 ga wire. I started the first pole, next to the ignition coils, and alternated the winding directions from pole to pole. I believe that my initial winding was in the same direction as the stock winding was. Does this sound correct? Thanks again.

I believe that my initial winding was in the same direction as the stock winding was.

This was what I was refering to. If you went the other direction on the initial winding and still alternated the winding directions. All would look right and it would work but would be less power output.

Sounds like you did it right than. I'm not sure what else to look for. I know it's a pain but could you swap stators and see if the problem moves with it to your other bike? Hopefully someone else could diagnose your problem better than me.


If you've wound all the poles with 18 ga wire the resistance will be too high. You would be better off to redo it and wind it in parallel, two sets of five poles. I did this on my last XR and it worked great. There is extensive information on this topic in the Files section of the XR650R Yahoo group.

This is some of the information taken from that site:


XR600/650R, parallel, lower resistance than 650-16, but more work to make it.


H: 0.483, W: 0.240, L: 0.438, poles: 10, depth: 6

Copper #18 ga. (insulated): 0.0423" dia, 6.385 ohms/1000ft

11 turns of #18 wire (0.465") fits in height 0.483"

6 perfectly stacked wraps (no interlacing) of #18 wire is 0.254".

Total turns = 660

Layer lengths (1-6): 16.8 20.5 24.2 27.9 31.7 35.4

One pole takes 156.4", 10 poles takes 130.4 feet

Stator resistance is 0.832 ohms at room temp.

Stator resistance is 0.996 ohms at 70C/160F.

Powering 55W bulb through this resistance generates 20.2 watts of heat

Powering 100W bulb through this resistance generates 68.6 watts of heat

*** Resistance may be too high to be useful ***

Consider splitting winding & connect two halves in parallel

Parallel res. (hot) = 0.249 ohms, equiv. turns = 330

Powering 55W bulb through this resistance generates 5.0 watts of heat

Powering 100W bulb through this resistance generates 17.2 watts of heat


I too rewound my stator with 18g for total of 320 wraps and have a 55/60W bulb in my BD headlight (complete BD DSK) and a totally dead battery. Even at idle my headlight is bright and handwarmers & signals work fine (blinkers a a little slow at idle. One thing I had to do with my rewind was place small 1/4 inch squares of friction tape between the wires where they cross between poles to bring my ohms down to spec (I think I scraped some of the thin laquer insulation off while winding between poles). That fixed everything. Hope that helps. I will later be replacing my battery as it is completely shot (won't even light the LED tail light with the engine off). Hope this may help you troubleshoot. BTW, does anyone have any suggestions for a replacement battery equivalent to the original one that came with the BD kit? Otherwise I'll be ordering another pretty soon.

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