1987 DR200 Lights blow

[hungrycamel]

I have a 1987 DR200 dirt bike with a taillight, headlight, and no regulator. The headlight bulb is 25 watts, the tail 5 watts. The system is 6 volts, AC, and no battery.

As it stands, the wires are routed like this: live wire from stator through the headlight, to the taillight, and then to ground (in series). The "ground" is about 5 wires meeting in a common splice.

My lights stopped working so I replaced the bulbs, and they immediately blew upon startup. I rode it for months without lights and started finally working on them tonight. 

Here's what happens:

If I crank it with the headlight installed and the taillight installed, the taillight ONLY will flash. If I start it fully, the taillight blows instantly, and the headlight never flashes.

If I short out the two leads heading to the taillight, the headlight only will flash when cranking. 

I cannot get them both to light under any circumstances.

Update: I just now wired them separately from the live wire to ground (in parallel). This causes both to work at idle, but revving past idle made them brighten, flicker, and blow.

Update 2: Okay, I think the PO messed up. Apparently the stator and the rest have separate circuits? There are two lighting wires coming from the stator; I had the black going to the ground splice and the live wire used as described. I just now separated the black wire and made this circuit (no taillight because I blew my last one): stator live > headlight > shorted taillight > stator black. The headlight worked fine and let me rev it sky high without blowing. I'll order a tail bulb and see what happens.

 

Can someone explain to me why this happens even if I kinda solved my own problem?

Edited February 13, 2018 by hungrycamel

[Richard Wagner]

Did your fix take care of the problem completely? I have the same issue. Both bulbs blow. The voltage ramps up over 20 when the engine is revved. I haven't really started troubleshooting. I assumed the system had a regulator, but can not find one in the OEM parts list.

[hungrycamel]

On 9/2/2020 at 2:49 PM, Richard Wagner said:

Did your fix take care of the problem completely? I have the same issue. Both bulbs blow. The voltage ramps up over 20 when the engine is revved. I haven't really started troubleshooting. I assumed the system had a regulator, but can not find one in the OEM parts list.

Never really did. Bought a TrailTech AC regulator to install to try to remedy the issue, but ended up selling the bike to a friend after the engine blew. I know the bike does NOT have a factory regulator, and I believe that the load of both bulbs in the circuit acts to regulate the voltage. I was reading that the old XRs used this system, which made it common for the other bulb to blow right after the first because of the increased available voltage.

I guess the harness I had was just wired wrong (definitely had been tampered with) or there were some shorts to ground causing the bulbs to blow frequently.

[Richard Wagner]

Thanks for the reply. I ordered several bulbs to troubleshoot with. Hopefully having both both bulbs does the trick. I will put some resistors in-line to draw some current if the bulbs blow again. 

[BillDirt1]

Is the bike factory equipped with a battery? If so, one in it now? If not, I'd bet that's the problem.

[turboguzzi]

add a simple 12v scooter voltage regulator, just chops off extra Vs

 

https://www.electrosport.com/collections/regulator-rectifiers/products/esr012-regulator-12v-ac

 

[Richard Wagner]

It does not have a battery.

I believe the bulbs are operating on AC voltage so I don't see a rectifier/ regulator working. I'll verify when the new bulbs arrive and I take the lights apart.

[turboguzzi]

exactly, it is not a rectifier

its an 12v regulator for AC, just what you need