AC/DC Wiring help needed.

Hi all,

I have a major headache with the wiring on my Yammy 02 WR426f and as a last resort i'm having to ask my fellow thumpers for the answers to my problems?

before i go into it, let me just say that i have searched all over these forums and although i have found some very useful info, i can't find the solution that matches my exact same bike or question. there are so many different opinions that after several hours reading i am now totally confused as to what i have to do to sort my bikes wiring.

let me explain:

as mentioned above i have an 02 WR426f (european) that has H/L headlights,tail/brake light/horn/neutral switch and indicators that come as std fitment on most European WR's i think? All these run on AC power from the stator into an after-market handlebar switch that has ALL buttons to work them, also has a combined kill-switch too. everything works as they should without any fuss, but here's the big dilemna.......... I want to add a Battery so i would no longer have to worry about the indicators/horn not functioning properly when idling etc, the headlight/brake and tail are ok but obviously they dip at idle too. i only use my street-tard on the road and i really would like to have proper functioning electrics and to do this i need to have a battery. I managed to get hold of a battery and wiring loom (harness) plus the reg/rectifier from an 03 WR450, and also a cd rom version of the 03 WR manual. Innitially i thought i'd just replace my loom with the 03 one, but changed my mind as there are many more connectors than i thought there'd be and most of the wires are different colours and far too many excess wires/connectors than what i'd need. so i decided to somehow add the battery into my current setup that would give me AC/DC for the headlight/tail & brake and DC for indicators/horn/fans etc. plus the ability to have working lights with the engine off 9which would eventually be wired into a keyed ignition/isolator switch.

Now here's the problem?

My AC output from the stator only has ONE wire (yellow) plus the 6 wired plug (CDI) but the 03's reg/rectifier has 4 connections, which i have come to understand is 2 into the reg/rect and 2 out to the + and - on the battery.

there's my problem! where do i get this other wire from? will i have to mod the stator (float the ground) that i've heard so many people on here mention but NO actual references explaining exactly if it HAS to be done or HOW to actually do it. most of the talk referred to older WR400's or converting to road YZ's as they have very little or no Wattage from the Stators etc. As i said before, my lights and everything are ok when riding, even in the dark the lights are well sufficient, it's just when on tickover they're poor and the horn sounds like a dying fly and the indicators barely light, let alone blink!

so, onto my questions (hopefully you've made it this far)

1: do i need to mod the stator to achieve AC/DC lights with DC indicators/horn etc given my current wiring setup?

2: what about the earths, should they all go to the battery apart from CDI/Coil?

3: would it be better to go for all DC lights/horn/indicators etc or would this be too much of a drain on the battery as i always ride with lights on during the day?

4: how would this affect the CDI if i went allout DC or would it not affect it?

5: if i floated the earth (from the stator) would that not stop the coil from working, as it earths on the frame or would i still need to have an earthed frame?

as you can probably tell, i am in quite a dilemna over this and i am at my wits end. I am ok at electrics as long as i have some sort of wiring diagram etc but neither the 02 or 03 manuals bear any relevant info apart from the 03 stator wiring diagram shows 2 wires coming out of it unlike the 02 which has only 1.... hence my questions..

I hope you guys can make sense of all this and what it is i am trying to do. I have researched and then some from the likes of Baja designs, trailtech etc etc but i am very confused and was hoping there's somebody out there who has added a battery to their 02 WR426 that has the exact same wiring loom as mine? here's hoping........... :confused:

thanks for reading anyway, lol.. :lol:

"Electric Start" ????? what a luxury that'd be?! i shouldn't be greedy i guess, i can start mine wearing me trainers! :crazy:

Save yourself some trouble and buy an aftermarket reg/rec from trailtech, next go to their website for any further information you'll need. They show picture diagrams of floating the ground as well as wiring schemesto show how the battery conncets to everything. It's really easy once you understand whats going on. Just float the ground (hardest part), run the yellow and white wires and connect them to the reg/rec, then run your ground to the negative battery terminal, and the remaining wire (red i think), to your battery. Now you can run everything off your + terminal if you want. And when the bike is on, the stator will charge the battery! Have fun

Best of Luck!

Hi, thanks for the quick reply....

I couldn't find any schematics/how to's on Trailtechs site with reference to the WR426/450', the only "how to" for the stator mod was for a KTM and i was hoping for something a little "closer to home"... i'll go have another look, but i'm sure i've been through every page?

for something that sounds an easy task, adding a battery, is turning out to be a bloody nightmare! i've completely stripped my whole harness off the 02 so i can rectify which wire goes where etc to ascertain how it's currently earthed?

I know the trailtech reg/rect puts out a quoted 150watts and the oem will put out 120, but the wiring is the same on both so what's the point of buying another one? basically i'm trying to imitate the 03 and latter WR's wiring as they have AC/DC, so is the stators earth "floated" on those models i wonder?

thanks anyway.. :lol:

I've just read my reply and i sound like a complete noob the way i had written the response! "ascertain how it's currently earthed?" lol... I should've refrained from my smoke before answering...

what i meant to say was..... which wire was "frame or engine" earthed etc.

but mainly to remove any uneccessary wiring and utilise the bare minumum required and to "tap in" for the battery feed.

Check out the BajaDesigns website.

I have a 2001 WR, and I floated off the ground so I could run the HID desert racing lights. I also wired in a battery.

BajaDesigns has an on-line manual that will help you figure out the wiring.

If you have trouble finding it, just shoot them a call.

I have found them to be VERY helpful.


Hi, have just had a look at BD and there's only a stator mod diagram for 03 onwards? can't find any info on the mod for our 01/02's plenty of info for the YZ's not WR426's?

So, it is necessary then to have to float the ground if i want to add a battery?

cheers :lol:


As mentioned, you'll need a single-phase rectifier/regulator from BD or Trailtech to create a DC powered circuit. Your 426 stator is single output, the 450 stator is dual output. The OEM WR450 rec/reg is not compatible with your stator because of this.

You can add a BD or TT rec/reg without modifying the stator however all of your DC grounds would need to isolated from the chassis which may not be possible with the stock harness (I'm not very familiar with the Euro-spec harness.) With this in mind, floating the stator ground to isolate the lighting coil from the chassis would probably be your best bet.

On your bike the ignition circuit is totally separate from the lighting circuit so there's really no chance of harming your CDI or any other ignition related component if you were to modify the lighting side of things. The black 6-pin connector from the stator directs everything ignition related, the single yellow wire is the lighting coil output. Modding the lighing coil will make it a two wire lead (each end of the lighting coil wire.)

Now my question is, if you were to add a DC charging system to your bike and interface that back into your stock harness, would you be able to turn everything off? Since your stock harness is setup to operate AC there is really no need for "off'" switching. With a battery there definitely is.

I wouldn't mess with anything but the lighting tap and the ground, all the otherelectronics can be left as they are.

you can buy a rectifier from your local electronics store that is rated to 35 amps and only cost a couple of bucks - this converts ac to dc, then go strait to your battery and then to your lighting circuit - this makes everything DC.

connect the ac side of the rectifier to the yellow from the stator and the other leg to the frame, then the other 2 terminals on your rectifier is positive and negative - connect these to your battery.

all your lights will need to go back to the battery negative, not the frame.

If you have any problems give us a yell.

Problem Solved.

that reminds me, i stuffed up a bit, install the rectifier after your OEM reg/rec. so that you still have a regulated output, dont install it directly off the stator because a full wave bridge rectifier that you buy from your electronics store does not regulate the voltage.

really, why buy a trailtech reg/rec that has and output of 150W, when you can just use your original one and have a rectifier after it to give you DC, and the rectifier is rated to 400V x 35A = 14KW. the battery will give you all the power you need for your lights etc and your charging system will charge that battery with 100W output of your stator + OEM reg/rec (20W is for the CDI) which is a seperate connection on your OEM reg/rec.

This is the cheapest and easiest way to do it, the only stuff around is to run wires from your lights back to the negative terminal of the battery.

your lights will never drain the battery because all up it pulls less than what your stator puts out.

the only problem with this setup is that your OEM reg/rec puts out 12-14VAC and that converts to about 10 or so volts DC, BUT your battery fixes that problem, it will keep your voltage at a 12V minimum.

I have done similar to this on my bike to power my GPS, i have a bridge rectifier with a 25V 2200 microF cap and a 12V regulator that is capable of 1.5A (which charging my GPS is powerful enough) This system is fine and only cost me a few dollars.

The only good thing about an OEM (or aftermarket) reg/rec is that the regulator side is capable of 10A (12V x 10A = 120W) and the little regs that you buy from electronics shops are only capable of around 1 - 2A. thats why the OEM's and Aftermarket reg/recs are expensive. So use what you already have and add onto it!

By the way, my WR is fully road registred and similar setup to yours, and with high beams on (acerbis twin headlight with 2 20W bulbs = 40W) my blinkers etc work when idling, but didnt when i got the bike and it had 2 50W globes in it.

thanks everyone who replied, lots of ideas, but ideally i don't want to have to mod the stator if can help it. I can understand the need to float the earth if i wanted to fit HID lights or to go "all out" DC.... but inorder to just have proper working Horn/indicators etc (DC) and leave the lights as they are (Regulated AC) then i can do as CR450X suggests and utilise what i've got.

So let me try and get this straight? i can swap over the original 2 wired regulator for the 03 4 wire reg/rectifier and to solve the issue of "only 1 wire from the stator" i can send the extra terminal (black) to a frame earth, and keep everything as it was but have ALL the lights power coming from and returning to the battery? is this correct? if so, would the lights be bright and would the battery also get charged? and finally.... where would be the best place to draw the power for the lights, direct from the battery + or would it be better to "tap" a feed into the output (from reg/rect) to the main switch as in a "T" junction sort of thing?

let me try and explain.....

1: fit the oem reg/rectifier inplace of the original regulator.

2: wire it the same as the original was. yellow AC (in) and black wire earthed to frame (as original was)

3: have the other 2 wires (out) from the reg/rectifier to the battery + and -.

4: connect the Main handlebar switch into the reg/rectifiers + (out to battery) or directly at the battery, either way is there any difference, (before the current gets to the battery or directly at the battery?) would the lights then be AC/DC?

but everything that is drawing power from the battery must earth back to it and NOT the frame?

is this correct?

if this works then it'll be a bonus as i can virtually leave the original wiring harness intact and just isolate ALL the earths from headlights/tail/brake/horn/indicators back to the battery - and NOT the frame.

i hope i've made some sense out of all that?

thanks guys..:lol:

I think i made sense of it, you wont need the 03 reg/rec, because you can just use the one you have now (now correct me if im wrong because i only know about the wiring on an 03 WR, and i think i understand how yours is wired).

Your stator has 1 wire that goes to your OEM rec/reg on your bike right now (and maybe another one for the CDI side) and the stator is earthed to the frame - that is the return path.

from the stator the wires go to your OEM rec/reg and from there you have a plug for your CDI and a wire that goes to you lighting circuit.

Now buy yourself one of these

you might as well buy that one, even though its capable of very high loads, they cost next to nothing so you might as well buy the best one.

The bridge rectifier has 4 terminals, 2 of them are the output + -, and the other 2 are the input AC, connect the wire from your OEM reg/rec (the wire that goes to your lighting circuit) to one side of the AC side input and connect the other side of the input to the frame.

then you have the + - terminals on your bridge rectifier - these go to your battery and this system now acts as a battery charger.

From your battery run the + to your main switch and bring all your lighting earths back to the - terminal of the battery.

Make sense?

This makes EVERYTHING DC, yes your battery will have enough power for your lights so wire it exactly how i said, let me know if you dont understand 100%.

Im an Electrician by the way so i know what im on about.

That's great, thanks CRF450X your spot-on with my wiring layout, that's exactly as it's currently wired apart from, it's not a reg/rectifier only a regulator, but i'm sure you know this already and it was a typo? :confused:

I'm sure i'll be able to get an equivalent reg/rectifier as the one you recommend here in the U.K?

But i thought i'd try the 03 oem reg/rec (now that i have it) and earth one of the inputs to the frame and connect the "outs" to the battery + and -, would this not work the same as the method you suggested?

thanks for all the great help guys. and thanks Rich for that link, now it's becoming a lot clearer what im trying to achieve when i can see the diagrams! :lol:

your reg on your bike is a rectifier as well only for the CDI output because the CDI runs off 12VDC, although dont use this output for lighting because if you have a short in your lights you could stuff up the CDI, the lighting output is 12VAC.

The part i mentioned to buy is definately available in the UK and is a rectifier only, not a regulator at all.

you can use the 03 reg/rec that you have if you want although you will still need to install that rectifier that i told you about so that it converts the AC lighting output to DC for the battery.

here ill inform you on a few things, our bikes have an OEM regulator/rectifier installed after the stator, the regulator side regulates the voltage to a maximum of 14.4V, there are two outputs on this device, a 12VDC output for the CDI (and battery + starting system on my wr450) and a 12VAC output for the lighting circuit, they are seperate so a lighting fault dosent upset the CDI.

lighting circuit has an output of 100W and the CDI circuit has an output of 20W

sooo, you need to install one of those rectifiers that i told you about on the lighting circuit so you get 12VDC, then go to your battery.

Now i am starting to get really confused (again)....

I've just had another look at my 02 wiring diagram in the manual and my wiring layout is as follows....

from the stator, i have.....

I started typin it but then i thought, why not just take a piccy of it from the manual. :lol:


any better?

as you can see by the pic, the CDI don't go anywhere near the regulator according to this diagram?

jeez my heads spinnin.......

would one of these do the job? but how the hell do i wire it in, as CRF450X suggests i wire it after my std 2 wire reg/rectifier, but how? I only have 1 wire (yellow) from the stator which goes into the reg/rect and one wire out of the reg/rect which goes to frame ground? so how can i use one of these.......

I am beginning to wish i never started this now as it is turning out to be more of a nightmare than i originally thought....

surely it can't be THAT hard to put a tap-in to my current setup so that i can have a feed for a battery, if by looking at my current wiring diagram in my last post and you see one wire to reg/rect then to ground, can i not simply replace that reg/rect with the 4 wired one that i have, so i would have 2 in and 2 out (for the battery)

but how would i wire it? anyone?

i'd hate to just give up on this and resort to having to bloody mess with the stators earth.....

i was hoping to get this done this weekend too :lol:

Mate, dont worry about the details, just do this....

connect the yellow wire from your OEM reg/rec to one terminal of the ac side of your aftermarket rectifier that i told you to buy and connect the other ac terminal of the rectifier to your FRAME!!!

Then the other 2 terminals on your aftermarket rectifier is DC + -

Simple hey???

and by the way - that link you have is exactly what you need to buy!!!

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