What's a BK Mod and Grey wire Mod ? ? ?

3 replies to this topic
  • humbertob

Posted January 10, 2002 - 06:56 AM


I wanna know what is exactly a BK Mod and Grey wire mod.......? May I make this mods in my '99 YZ400F....? I'm reading so much about these mods here but I got no idea what are all about ?

Thanks for your answers ! :)

  • skthom2320

Posted January 10, 2002 - 07:54 AM


You cannot do the Grey wire mod. That is for WR models.

You cannot do BK mod, that is for 2000-up models. However, you can do something similar to the BK mod for your bike. See this thread BK mod for 1998/1999 started by NH Kevin. Basically, your carb accelerator pump generally throws too much gas in when you wick on the throttle - there is a 2 or 3 second stream thrown. You can limit this to about 0.5 seconds by shortening the throw of the accelerator pump. On the 2000-up bike there is an "ear" or tab on the side of the carb that you can drill and tap to palce a set screw to shorten the throw. On the 98/99 there is no tab but the thread above give ideas on how to shorten this throw...

Picture of the BK mod are on motoman393's web site which will give an idea of what is happeningclick here


Steve T

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • gerry

Posted January 12, 2002 - 10:55 PM


I own a 2001 wr426 what is the grey wire mod and how do i do it

  • skthom2320

Posted January 12, 2002 - 01:29 PM



I don't have a WR so I can't give you good information. But if you go over to the WR side of Thumpertalk and click on the word "search" in the upper right of the screen, you can enter "grey wire" to get more info.

Basically it's a grey wire that runs underneath your gas tank. I think it has something to do with retarding the ignition or timing. If you cut it, you will have immediate performance gains.

I am not sure if non-US bikes have this wire...


Steve T

Related Content


Thinking about Yamaha 250... by Arctic Pride

Dirt Bike   Special Interest Forums   Pro Racing
  • Hot  491 replies

YZ450F 03 Sparks driving me crazy by SirAttard

Dirt Bike   Make / Model Specific   Yamaha   YZ 400/426/450
  • 5 replies

yz250x vs 450 4t comparisons (preferably desert riding) needed by JakeNorthrupYZ450F

Dirt Bike   Make / Model Specific   Yamaha   Yamaha 2-Stroke
  • 9 replies

Michigan Motocross Tires by 288yz450

Dirt Bike   Dirt Bike Regional Discussion   North
  • 1 reply

2016 YZ450 by CaptainKnobby

Dirt Bike   Dirt Bike Technical Forums   Suspension
  • Hot  59 replies

Join Our Community!

Even if you don't want to post, registered members get access to tools that make finding & following the good stuff easier.

If you enjoyed reading about "" here in the ThumperTalk archive, you'll LOVE our community. Come join ThumperTalk today!

The views and opinions expressed on this page are strictly those of the author, and have not been reviewed or approved by ThumperTalk.