BK mod on 00 wr?

why doesn't the bk mod work on the 2000 wr400?

I think there was a small misunderstanding a while back because the mod does work on the 2000 WR (not on the 98/99). I was reluctant to do it as I felt (after many, many adjustments) that my bike was jetted perfectly. I therefore put it off until right before winter storage time. I raised (enrichened) the needle one clip as James Dean suggested and adjusted the stroke to about .5 seconds. All I can say is - Jeez - I should have done this sooner! The improvement was staggering, third gear wheelies, and I'm not the smallest dog in the litter. I can only thank everyone (especially JD) as this bike runs absolutely fantastic. The only real question is, with your P38, do you really need to do it? I'd start by measuring the stroke. Make sure and go to full throttle quickly with the float bowl full. Mine was over two seconds! Good luck..


I believe the P38 does NOT allow you to alter the timing of the squirt, just the duration (total volume). This is the other CRUCIAL advantage of the BK Mod.

Can someone send me some pictures and instructions of the bk mod for my 200 wr400?

Hey motoman on this site it says that it will not work on a 2000 wr400? I'm confused.

I think this summarises it correctly

#1) BK mod :works for 2000+

#2) KL mod : works for 98,99 also 2000+ but why would you if you can do the BK mod??

#3) Disconnect apj : all models but jetting !!!

#4) Bracket KL/BK mod 98-2002

#5) P38 lightning : all models (Wont change timing, just duration.


OK! you talked me into it! My 2000 WR will be BKed soon! :D had to let the dust settle and get all my facts straight. about .5 sec? she is jetted well now.. 175 MJ 45 PJ (pretty sure, will dbl check.) should I expect to need to change? or should i mess with clip setting first? thanks a lot guys! :D i don't know what i would do without all of you! (except BennY :) )

thanks again :D

OK I did the bk mode today. when I put the carb back on with the new set screw not touching the linkage it would not squirt fuel when throttle was twisted.I put the pipe on and started it up, let it run for a minuite and shut it off still only one short squirt of fuel then nothing.

Also the pump linkage doesn't move much to begin with, about how much do you limit it's movement to approximately?

[ November 26, 2001: Message edited by: robman ]

Robman, I see you now have the P38 lightning mod and also the BK mod. ! I have no idea if one will help/interfere with the other. Anyone?

From a SQUIRT POV my understanding is that you should only get this squirt from 0 throttle upwards and only for about 0.5 secs optimal. If you dont go down to 0 throttle again it probably wont squirt ? This from memory and interpretation as I have not done either ...I have no APJ funtion at all....disconnected.


Yes missile it only squirts once per throttle opening but on the second throttle opening it did not squirt any fuel, I think I've got it worked out though. I think the p-38 interferes with the pump because before I did the bk mod it would only squirt for about 1.5 seconds anyway.I think I've got it down to about .5 I think.and the pump timing is set so that the squirt just misses the slide.

If anyone has any other comments or suggestions please let me know.

Thanks for all the help.


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