grey wire confussion..

I bought a 2005 wr450 from Berkeley Yamaha....they did install a yz throttle stop but left the grey wire intact? When asked they said to leave it alone, although everything I have read says to disconnect it...who should I listen to and how do you do it?

I bought my bike form Berkeley Yamaha too and they also did the throttle stop , i would leave the wire on, mine dosent run as well with it disconnected, thats just MHO

In my experience the grey wire makes a big difference if you have done the cam mod. :p I have not tried it with the wr cam timing. :) But with the cam mod, airbox opened up, throttle screw and the exhaust opened up the grey wire should let the engine rev all the way up to redline and pull all the way there. The grey wire is just a ground that tells the ignition to use the wr ignition maping. If you disconnect this it will tell it to use the yz ignition map. It definately made a difference on my buddies 05 wr450 with all the mods and proper jetting.....He was afraid to do the mods so I did them for him... :)

When I bought mine it seemed like it had more power down low before I disconnected it.

Its probably all in my head, to tell you the truth Its hard for me to tell a big difference when I only do 1 mod at a time, when I did my jetting and my exhaust those were huge gains in performance.


it seems as if yamaha has told their dealers to leave the wr's stock as of late. i don't know if it's a warrenty issue or backlash from some of the '03 problems. it's a wonder they even did the throttle screw. use the "search" feature of this site. so many new guys seem to ask the same questions over and over without checking for previous data. you'll find all the how to info you need. that said, there is no reason your bike shouldn't run alot better with the grey wire disconnected. it's all in the jetting. you shouldn't loose anything on the bottom and should pick some up on top. when i say top, remember, wr's have a red line of about 10,000. you'r going to feel the increase when you really hang it out. like when it's time to show your buddies just how fast your bike is. one thing to remember is that your bike has to breath to run well. if your not going to open up your air box (at least the snorkel in the airbox) and your exhaust, don't bother with the wire. all the mods work hand in hand.

Search this forum for jetting help and go to ThumperFAQ for details on lots of mods to improve your bike. It's a 250F site but just about all the mods apply to the 450F. This includes the grey wire mod which they have a pretty good explaination of including graphs of the ignition curve and horsepower with and without the grey wire connected.


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