DR500 voltage regulator??

I've been a long term lurker on ADVrider, but have never had anything interesting to add. So it annoys me greatly that my first real interaction is to plead for help!
But, here goes.
I've got a 1981 DR500 that I'm currently building with a homemade sidecar for a charity ride later in the year (Scrapheap Adventure Ride 2015 if anyone's interested). Everything is coming along fine, except for the electrics. With the engine idling it reads 9 volts across the battery and keeps blowing headlight globes after a short run. So I worked out the rectifier is OK, but the regulator isn't. The regulator and rectifier on these things are separate items. I tried ordering a new reg. from the local Suzuki dealer and after a first try failure, they told me it will be $208 with a six week wait from Japan. That's probably only about US$3.99 and not a worry. But it equals around 14 Dingo skins and your left testicle over here!
From what I can make out of the wiring diagram, the reg. is basically a resistor. So what I'd dearly like to know is, could this be made up with parts from the local resistor shop? What value impedance etc? Also, would a new reg. be available in the US?
It's really the only thing stopping my progress on the build, but it is stopping me!
Any help/advice you guys can offer will be greatly appreciated

T.I.A.
Russ
maybe a Zener diode instead of a resistor. hard to find an aftermarket replacement with a high enough power dissipation to be safe. I used to put Podtronics and Tympanium regulators on vintage bikes. they are R/R combos & both work great, the pod is better looking if you care, in any case I 'spect might work for you.

search Tympanium and dozens of sources will pop up, (edit:just looked... Tymps are about 50 bucks on ebay)

http://podtronics.net/

can you post a diagram?
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As I don't have a scanner, I hope this pic is legible.
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Here is the regulator as mounted on the bike
I'm I'm no electrical genius and I don't play one on TV, but it looks like that's an AC regulator. Hondas from similar vintage do the same thing. They used a rectifier to convert to DC and then dump that into a battery and use the battery to "regulate" the current to the tail light, brake light, winkers, and horn. Then they use an AC regulator on the power from the stator that feeds only the headlight.

I've got a 1980 xl500, which has a 6v system. I kept blowing headlights do I installed a headlight from a postie and use a 12v bulb and I installed an AC regulator on that leg from the stator. So what I ended up with is a bike with 6v tail brake and winker lights and a 12v headlight.

I think I paid about $20 US for the AC regulator I used, but trail tech has a better one that you can adjust the voltage a bit to get longer bulb life or brighter output.
If you replace the "resistor" (it might really be a zener diode anyway) with a 6V zener diode they can be paralleled if need be but they must be matched, FWIW some of the last of the Norton Commandos with higher output alternators worked that way and used two 12V zeners in parallel...if they are poorly matched one will take all the load and burn out. Modern zeners might be a good match as is since components are more consistent these days but it would be a good idea to test them first, maybe buy several and use two that match best....or perhaps you will be able to find a single zener that can handle the current/power. FWIW on Nortons a single zener was used for 120W alternators and two for 200W units IIRC.
The Podronics unit is very popular in the British bike world but it converts 6V Lucas systems to 12V, it might or might not work that way with your Suzuki alternator.
http://www.burtonbikebits.net/PODtronics insturctions.htm
well.... I think it's DC. simple way to tell is if the headlight comes on when the engine is off. heres what it looks like to me.... Red from the battery (and rectifier) goes to the IGN switch & becomes Orange when on. that feeds the Light switch (on/off) and that feeds the Dimmer Switch (Hi/Lo). center wire (B/W) of the headlight is going to ground at multiple points.

the "Resistor" may in fact be a resistor. it is only connected in the circuit when the headlight is off.... that would provide a (somewhat) equivalent load.

I don't see a regulator at all....

so next thing is.... what voltage is it supposed to be?

as for useing a zener... that would work but it needs to be the proper voltage. zeners in parallel can share the load but as mentioned, the one with the lowest value will hog the current. zeners in parallel will still react the same as alone.... not like resisters. multiple 12v zeners in a 6v system won't make a difference.... they will all block until you get to 12v.

another thing...a zener in the AC side will still conduct 1/2 of the sine wave, so that simply goes to ground as heat. you would want the zener in the DC side

the best way to use the Tympanium or Pod would be to go into the generator and remove the lighting coil's ground off of the stator. right now thats making the AC ground go through the frame. once lifted, the 2 AC outputs can go to the RR and the 2 DC output can simply go to Red and frame. I have done this to vintage enduro bikes
Beezer said:well.... I think it's DC. simple way to tell is if the headlight comes on when the engine is off. heres what it looks like to me.... Red from the battery (and rectifier) goes to the IGN switch & becomes Orange when on. that feeds the Light switch (on/off) and that feeds the Dimmer Switch (Hi/Lo). center wire (B/W) of the headlight is going to ground at multiple points.

the "Resistor" may in fact be a resistor. it is only connected in the circuit when the headlight is off.... that would provide a (somewhat) equivalent load.

I don't see a regulator at all....

so next thing is.... what voltage is it supposed to be?

as for useing a zener... that would work but it needs to be the proper voltage. zeners in parallel can share the load but as mentioned, the one with the lowest value will hog the current. zeners in parallel will still react the same as alone.... not like resisters. multiple 12v zeners in a 6v system won't make a difference.... they will all block until you get to 12v.

another thing...a zener in the AC side will still conduct 1/2 of the sine wave, so that simply goes to ground as heat. you would want the zener in the DC side

the best way to use the Tympanium or Pod would be to go into the generator and remove the lighting coil's ground off of the stator. right now thats making the AC ground go through the frame. once lifted, the 2 AC outputs can go to the RR and the 2 DC output can simply go to Red and frame. I have done this to vintage enduro bikes
I said maybe try using use 6V zener diodes above, NOT 12V, only mentioned the Norton arrangement by way of example of how zeners are sometimes paralleled and need to have matched performance when paralleled. If the resistor (or whatever it is ) is only in the circuit when the headlight is off that would not explain why the OP is blowing headlight bulbs.
Thanks for your help guys. Just a thought, what if I took the purple wire from the magneto and ran it straight to the red from the battery instead. Then did away with the resistor. Would that work, or would it be too much load on the magneto?
purple to red.... no. red is DC, Purple is AC... it would have to be rectified first. also, without the diodes.... when the engine isn't running, the battery would dump into the generator windings. the diode(s) in the rectifier also blocks reverse current with the engine off (on the R/W wire)

as for the resistor... it's on W/G wire. follow that to the lighting switch. you can see that it only connects to power (W/R) when the headlight switch is "off". that means as long as the headlight is on, the resistor isn't on the system anyway

and ya.... none of that explains why the headlight is cooking. so basics... is it the right bulb? and is the battery good? I know these older bikes had problems blowing bulbs if the battery was weak or the connections were poor
The battery is brand new so I guess I'm going to have to go through and check a whole lot of earths and connections.
I might even try and run a 12v headlight globe to see if it blows or not.
Hello Nudie,
haven't read every detail as I'm preparing for an Easter-visit to friends ...
Is your DR 500 still 6 volt? Maybe it's electrical-system is comparable to the one on our GN 400 (street-sister of the old DR 400 from the 80-ies). A friend from our German GN-Forum developed an upgrade to 12 Volts and maybe, this could solve your probs.
If you answer that 6-volt-question with 'Yes' I'd take a closer look at your and my wiring diagram to see if my friend's conversion might work on your bike. And if the description of the work necessary in our German Forum translates well enough into English ...
But you'd have to wait 'til tommorow ...
Kind regards, Bambi
Hi Bambi, yes it is still 6v. All original except for the exhaust.
Thanks for any help you can give!
Hello Nudie,
for a better (easier for me) comparison: our GN 400 is equipped with two electrical resistors, embedded in porcelain. I haven't found something like that on your diagram. But I have to admit, that I'm rather close to an electrical fool ... ... but I still managed the conversion of our second bike all by myself after seeing how it's done by my friend on our first bike.
Our bike 'regulates' it's volts by the amount of the consumers engaged (hope, I used the right or at least understandable terms). Those resistors come into action when I switch off the lights ... Surplus electricity is changed into heat and taken away by air-flow. Something like the zener-diode on my Meriden Triumph ...
Kind regards, Bambi
Sorry, I Forget to mention:
There's a bit of a difference between the 500 and the 400 cc bikes. As far as I do know your's is said to have an output of 90 watts and our's just 60 watts from the alternator. We have to have an eye on that!
More regards, Bambi
Thanks Bambi!
Nudie, as mentioned earlier it might just be a zener. However what puts me off this theory is the fact that when a zener diode malfunctions, it just produces a simple short, which means, no matter what the voltage is, it’ll just be a short. Please note that you can individually test the alternator by mounting it some other bike to check if produces a correct output voltage. Only by individually testing the components, you can get the correct diagnosis.

circuit board manufacturing
Hello Nudie, hello there,
sorry, I've been a bit quiet the last weeks. But in the meantime I learned that a mate of mine is rebuilding a DR 500 S. I'll talk to him to compare the electrical components of the DR 500 and our GN 400 to see if that 12-volt-conversion of the GN might work.
Riding the GN at night a few days ago brought back to mind how good that conversion works. Headlight, fitted with a H 4-bulb is brighter than that of my DR 750 Big! The output only drops when the engine is reving below 2.000 turns. And you can even watch the reflection of your turn-signals on the back the car in front of you at daylight!!!
Kind regards, Bambi
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