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Help headlight getting to much juice

By tribalbc,
in WR400F/426F/450F

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Grand Master

tribalbc

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So I've had a front # plate up front rather than the headlight all summer and I went to hook up my light again.

First my two wires for the headlight connection were frayed from rubbing on the steering head so I put some new connections on the wire and plugged her in.

Fired up the bike, the headlight was very strong for about 30 seconds, flickered, and then the bulb blew up.

It was the stock bulb, so I thought maybe it was it's time, so I threw a new 45 watt one I had kicking around. Fire up the bike and same thing....

I can't find any other fraying or shorts on the wire harness at the steering column so any ideas?????

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Grand Master

grayracer513

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Looking at the schematic, the feed to the headlight runs straight off the stator with no regulation of any kind. I don't know why it would suddenly be producing more power than before, but if this continues to be a problem, you could run a power feed to the lamp from the red lead at the rectifier/regulator. That would give you a managed 12v DC. Naturally, you'd want a switch, since the lamp would run from the battery.

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Proficient

miweber929

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Your regulator is blown out. On the WR the regulator/rectifier regulates both the AC and DC magneto's. If you connect the headlight to the red lead your battery will be dead in very short order. The DC output is only about 2 amps.

+1

Frayed wires created a short to the regulator until it fried itself would be my call.

Mike

Edited by miweber929
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Grand Master

grayracer513

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Your regulator is blown out. On the WR the regulator/rectifier regulates both the AC and DC circuits.
There is no DC magneto, but there are two distinct circuits. If the regulator acts on the AC side, it must do so by shunting excess voltage to ground, then. That's not obvious from the schematic, but it's certainly possible.
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PBDBLUE

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There is no DC magneto, but there are two distinct circuits. If the regulator acts on the AC side, it must do so by shunting excess voltage to ground, then. That's not obvious from the schematic, but it's certainly possible.

Yes there are two magneto coils. One (the white wire) supplies the rectifier and becomes DC for the battery. The other (the yellow wire) supplies AC to the headlight. And yes it is a shunt to ground regulator. The AC shunt regulator is incorported in the same regulator/rectifier housing. It's pretty common for them to fail.

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Grand Master

grayracer513

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Yes there are two magneto coils.
Sorry. I'll give you the regulator, but there is no such creature as a DC magento, in the first place. DC generators can only be accomplished through the use of brushes and a commutator. All simple magnetos produce AC voltage because the magnets involved have two opposing poles. DC voltage is only achievable with such devices by using a rectifier to either filter out the inverse polarity (half wave), or to invert the inverse polarity and add it to the forward polarity (full wave).

The fact that there are two coil sets within the single magneto changes nothing. They are simply twelve coils in series, grounded somewhere between the ends. Both circuit segments produce AC voltage, in spite of the fact they are electrically separated. It is only the presence of the rectifier that changes that on one of the two.

The bike could as easily have been wired with the coils in a single set, but the way it's done is a simpler way to satisfy the daytime running headlamp requirement with fewer electronics.

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Grand Master

tribalbc

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Thanks guys. From looking at my schematic it seems to run through the regulator and this was my first thought, was looking to confirm. That was my suspicion that the frayed wires had shorted out and blown the regulator.

Electrical certainly isn't my strong point so I was looking for opinions.

I don't have the best circuit tester, manual calls for AC20 to test, best I can do with mine is AC50, and I'm seeing 20V at mid rpms.

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PBDBLUE

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Sorry. I'll give you the regulator, but there is no such creature as a DC magento, in the first place. DC generators can only be accomplished through the use of brushes and a commutator. All simple magnetos produce AC voltage because the magnets involved have two opposing poles. DC voltage is only achievable with such devices by using a rectifier to either filter out the inverse polarity (half wave), or to invert the inverse polarity and add it to the forward polarity (full wave).

The fact that there are two coil sets within the single magneto changes nothing. They are simply twelve coils in series, grounded somewhere between the ends. Both circuit segments produce AC voltage, in spite of the fact they are electrically separated. It is only the presence of the rectifier that changes that on one of the two.

The bike could as easily have been wired with the coils in a single set, but the way it's done is a simpler way to satisfy the daytime running headlamp requirement with fewer electronics.

Well ok I guess I wasn't clear. There are two coil sets connected together at the ground which provide two AC outputs. One of these gets rectified to provide DC to the battery. Hence I called it the DC magneto only in that it is part of the DC circuit. Yes you are right it could have been done with one coil but the dual coil setup is the stock setup used by most manufacturers (Yamaha WR, Honda CRF and KTM XC/EXC for example). I'm not defending the method just trying to explain how it's wired so he can fix his problem. The aftermarket conversions generally provide one output of higher capacity and run the entire bike on DC including the headlight. The only downside to doing so in the case of the WR is that once you convert it to full DC the bike will not run if the regulator fails and the battery goes dead. That's not true of the CRF and the EXC as they have a seperate magneto just for the ignition.

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Grand Master

tribalbc

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The aftermarket conversions generally provide one output of higher capacity and run the entire bike on DC including the headlight. The only downside to doing so in the case of the WR is that once you convert it to full DC the bike will not run if the regulator fails and the battery goes dead. That's not true of the CRF and the EXC as they have a seperate magneto just for the ignition.

This is interesting as I figured this was an excuse to go to an aftemarket stator and regulator to get some real lighting power.

What you said was almost a deal breaker for me but then I remembered my bike won't work with a dead battery anyways, the CDI needs some DC juice.

So either way if my regulator should fail on the DC end I'm SOL.

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Grand Master

123BigcoopDawg576

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The only downside to doing so in the case of the WR is that once you convert it to full DC the bike will not run if the regulator fails and the battery goes dead

Yup, until the battery is dead the bike will still run like normal?

So either way if my regulator should fail on the DC end I'm SOL.

You'd be surprised how far you can right on a WR with only the battery and a failed reg/rec :banana:

In 07 my Dad and I were on our (at the time) 06 WR's...We both had the Baja Designs stator mod and Reg/Rec.

About 200 miles into a 5 day Baja ride (we were in the middle of BFE) his bike dies and wont start...:banghead:

We did some testing and realized the battery was DEAD and also notice he was not getting any DC power from the reg/rec

The only option for us was to swap batteries. The idea was to let my bike "charge" the dead battery and he could at least ride until the battery died.

Well out of 800 miles, we only swapped the battery on more time at the 600 mile mark of the trip. With out running any lights, he was able to ride 400 miles on a fully charged battery before it was dead. Needless to say, we finished the ride :worthy::foul::banana:

Dont be afraid to convert over to DC...You will find that your battery will stay charged A LOT better, you will have tons of DC power for lights :ride: and IMHO its extremely reliable :ride:

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PBDBLUE

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This is interesting as I figured this was an excuse to go to an aftemarket stator and regulator to get some real lighting power.

What you said was almost a deal breaker for me but then I remembered my bike won't work with a dead battery anyways, the CDI needs some DC juice.

So either way if my regulator should fail on the DC end I'm SOL.

The stock magneto setup uses the magneto that powers the headlight to power the cdi so you don't need the battery or DC for the bike to run. It won't estart but it will run. Once you convert to a single magneto then the cdi gets it's power from the rectifier or battery so if no DC it will not run. Like 123BigcoopDawg576 mentioned the newer aftermarket stuff is much more robust so it's less likely to happen. Really a personal choice. IMO if your don't need additional DC to run something like an HID headlight I would leave it stock. The reg on my '04 WR failed the same way as yours (i.e. no AC regulation). I found a used one from a YFZ450 (quad) on Ebay pretty cheap. Same unit but the leads are shorter so I just spliced on the cable/connector from the old reg.

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Grand Master

tribalbc

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The stock magneto setup uses the magneto that powers the headlight to power the cdi so you don't need the battery or DC for the bike to run. It won't estart but it will run. .

Well from personal experience I have twice had a dead battery on my bike and it will start and run, but not make any power or go over 4500rpm. You can barely limp her home over flat ground. From what I understand, the CDI needs some power from the battery.

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Grand Master

tribalbc

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It sounds like in your case the battery may have shorted. Did you try disconnecting the battery when it failed? There are a ton of posts on here about running the bike without the battery and starter.

Well the first time was when I first had my ebatt and didn't have it hooked up to the charging system. Worked great till one day I killed the battery.Recharged it, hooked to charging system and never had a problem.

Second time ground to battery came loose in a race. Same syptoms, fixed ground, good to go.

I know the older WR's can run without battery but I was under the impression that the newer ones need the bat??

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