The '' grey wire '' everybody refers to is a tach signal to the c.d.i. unit. It modifies ( retards ) the ignition timing map. When it's disconnected the timing advances, and ( I assume) more closely matches the YZ timing.I don't believe it affects timing at kicking speeds, so it should have no affect on starting. I may be wrong on that point but I know my 426 starts very much the same either way, and it runs notably stronger disconnected. Jonny426
There seems to be quite a bit of info on the WR400F forums. It is on thumpertalk.com. It seems the grey wire is used on states only WR's and people think it's there to meet noise levels, as it changes the timing right at the RPM the sound check is performed at. Who actually knows?
What we dont know for sure:
Why Yamaha put the gray wire on U.S. only WR bikes. The genral thought is that it was to meet sound test. With the throttle stop stock the gray wire retards timeing at what would be close to full throttle.
What we DO know for sure:
The mod has not hurt andy CDI boxes.
Non U.S. bikes have the gray wire but it is not connected. Maybe reason for diffrent non US needle in carb.
The mod most improved 01 WR 250F and 01 WR 426F, 00 and 99 WR 400s did not notice a huge differance, but did notice it.
It is a FREE mod and you should do it and be happy and not ponder why it was there in the first place.
you guys are all wrong! being new to the board i almost feel out'a place posting this,but here goes. the grey wire? it's the differance between showing up to the kegger or later,running around with your pants down,chasing the local chief of polices 16 yr old daughter yelling the yellow rose of texas.the differance between showing up for your blind date,dressed in levis and a t-shirt or having some strange(but hot) woman from your condo jumping off the second floor balcony,in a black lace teddy,and landing on you ,kissing and hugging you because she always thought you were hot.the differance between voting democrat or getti'n your head right and voting for me!;) that's the diff between not, and then cutting they grey wire. sorry fellas, gotta work my creative writing for inmates, or i go back to toliete dutty.the grey wire cut is gooood.
Uhhhh,,, yeah,,, ummmmm:::::: ok Crash, ok,,, Hey SFC, when you check your fuel level in the tank, it is adviseable to keep your nose and mouth a few inches away form the vapors :) . I am not sure about the rest of SFC, s post, but the last line seems to be accurate :) .
I guess I've had my head stuck in the sand since I got my '99 WR, because I don't remember seeing this "gray wire" info on them earlier. I saw it for the newer bikes like the 426 and 250F. So, while changing from my IMS tank to my YZ tank the other day, I looked for a "gray wire" I found a wire I thought was black on the black connector from the CDI. Is that it?
No, the gray wire is not black :) . It is ,,,,,,,,, well,,,,, gray. Its on a two wire connector, its the ONLY gray wire on the bike, Its under the tank unless the wiring has been rerouted. It is on the 99 US WR cause thats what I have :) .
It absolutely makes a difference in how your bike pulls in the mid range. I waited and waited to do it, read the TT thread 20 times, and finally got the thing disconnected. Made an immediate improvement. Dont cut it though, simply push the connector pin away so it doesnt make contact.
This is what I say about the grey wire cut on my 2000 WR400. The power increases in the mid to upper range. The power is more electric like and it seems to rev a little longer. It removes most but not all stubble.