400 injector pump bk mod

how or is it even possible to do a bk mod on a 400 fcr carb :thumbsup:

This info was copied from Garrett Bergs website regarding the BK Mod:


This accel pump mod is ONLY for the 00'-02' YZ426, 01'-02' YZ/WR250F and 00'-02' WR400/426) this WILL NOT work on 98-99 YZ400's and 99 WR400's.

I hope this helps.

I just performed the BK mod to my 2000 WR400F on Sunday. Detailed instructions can be found within these forums or in the 250F FAQ's. Once you find good specific instructions and remove the throttle cable cam cover from the side of your carb to reveal the accelerator pump linkage, it will be obvious where to drill the hole and how the mod changes the duration of the AP squirt by providing a mechanical stop for the linkage. The mod is very simple.

Good luck,


if u're using a 98 wr400f carb, bk mod doesnt apply.. wat u need to do is a 'taffy mod'..do a search on it..cheers..

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