99 WR 400 New owner.Grey Wire?

Im under the impression this mod dosent apply to us 99WR400 owners.

Only folks with newer bikes (2000 and up) :)

I see allot of peaple mention that they have cut their grey wire. What does that mean?

Do a search under "grey wire" or "gray wire" and you'll find a wealth of information for your reading pleasure.


Here is some good historical info on the gray wire mod:


I put a small toggle switch in-line on my 98 YZ timed WR when this subject came up last year to evaluate any changes in performance while riding. I found the mid-range throttle response to be slightly crisper with the gray wire circuit open vs. closed. I have since removed the switch and now run it with the gray wire clipped, capped and stowed. It is important to note that this mod is NOT a substitute for good jetting.

The most reasonable sounding theory I've read of why this circuit exists is it was Yamaha's way of making the US bikes run slightly less crappy with the throttle stop and airbox lid in place. Is there anybody out there that can verify this?


I should have mentioned that I have a Canadian

model witch I'm sure didn't come with the throtle

stop ,but hey I'm new to the 4 stroke world.

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