07 WR450 auxiliary power source for system checking.

I have an 07 wr450 that has had a lot of the electrics disconnected / removed.

All it currently has is tail / stop light, head light and a Vapor speedo.

I want to get it road legal and need to figure out where all the wiring and connections are for the horn indicators, neutral light etc.

My question is can I hook up a 12v car battery to the rectifier output or similar location to power the DC system and enable me to multimeter check the wiring and switches when live.

I am hoping this would give me power to check the system without having to actually start the motor all the time.


I first suggest getting a shop manual. I would then use a meter ohms setting to confirm wiring and connections.


I'd connect the battery (with a 20amp fuse) to the bike at the OEM connection points and test again, this time for voltage levels.

I'm confused a little on this one.

Your bike came standard with a battery, right? Why not just start with hooking it up, and putting it on a charger so it recharges while you aren't working on it?

If your wiring is a mess, it may be worthwhile to consider a replacement harness. Are you talking about a street legal one from the factory? I know I can find a new harness for mine here for about 65.00 US plus shipping, of course, mine is a lot simpler than yours if it is OEM With signals and such.

Sorry if I my first question was confusing, it’s a bit hard to explain what I was thinking without writing an essay.

I guess my original post should have also asked.

Do / should the indicators, horn etc work when just the ignition is on or does the engine need to be running?

I ask this because it seems a bit weird as my break light will only work when the engine is running yet the tail light works with just the ignition on and the motor not running (Has the OEM LED taillight assy).

This led me to think that maybe the rest of the DC electric system may run straight from the magneto / rectifier and that the on board battery is only for ignition and the e starter?

The headlight obviously only lights up with the motor running as I believe it is feed straight from the AC magneto via the regulator.

My question about the auxiliary battery was me thinking that if the engine needed to be running perhaps I could just use a large car battery tapped into the correct regulator output to “Trick” the system into thinking the motor was running instead of starting it all the time to get electrical power. It would then be much easier for me to multimeter my switches etc.

Yes it was a street legal WR from factory and the main harness seems to be all there.

I do have a manual but find it a rather crap in regards to the wiring schematics.

In that case I'm not sure. In California the lights are required to be able to be on for a minimum of 15 minutes without the bike being on.

I have a WR426 without a battery. I just hooked one into the wiring harness to do exactly what you want to do since having it running wasn't optimal. It worked for me, but YMMV.

Your bike should have a battery on it. No battery, the turn signals will not work nor the horn.. Sounds like the brake light is on the AC side of things.

On a WR, the CDI is DC, and is fed from the battery, whcih is charged by the Reg/Rect (controls voltage and converts AC to DC) which is powered by the stator (which makes AC). Interestingly, if you look at the wiring diagram, the LED tail light is wired into the CDI.

And no, you cannot fool the Reg/Rect into thinking the engine is running.

Go here to get a more complete basic wiring diagram

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