Throttle Response



12 replies to this topic
  • Mr426f

Posted April 11, 2016 - 03:43 PM

#1

Hi, My name is Tre, Just recently joined this grou.. Like 10 mins ago lol just have a question! Are people still doing BK mod or Oring mod?

  • Krannie McKranface

Posted April 11, 2016 - 03:49 PM

#2

Hi, My name is Tre, Just recently joined this grou.. Like 10 mins ago lol just have a question! Are people still doing BK mod or Oring mod?

Yes.

Depends on the specific carb

A stiffer pump spring is a better option (FCR MX/CR only)



  • Mr426f

Posted April 11, 2016 - 04:10 PM

#3

2002 yz426f ?

  • Krannie McKranface

Posted April 12, 2016 - 08:21 PM

#4

2002 yz426f ?

http://motoman393.th.../tech/carb.html



  • cowboyona426

Posted April 13, 2016 - 05:40 AM

#5

Not much chatter these days about the old BK mod.  Most guys have probably either done it by now or have no idea what it even is.  I never noticed a tremendous difference when I did it to my old 00 YZ426 but I'm not a jetting expert.



  • grayracer513

Posted April 13, 2016 - 06:22 AM

#6

The main thing is pump squirt timing per the manual.  Most of the problem with the 426 was the squirt was too long and too early.  The O-ring mod shouldn't be used on the 426, and for 450's, the heavier linkage spring mentioned works better.



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  • Mr426f

Posted April 14, 2016 - 09:52 AM

#7

Kind of a nob to this but where can i purchase stiffer linkage spring

  • grayracer513

Posted April 14, 2016 - 11:14 AM

#8

I doubt they exist for a 426.  But the problems with a 426 was not, for the second time, a matter of a weak accelerator pump shot, it was too long a squirt duration, and too early. 



  • Mr426f

Posted April 14, 2016 - 11:35 AM

#9

So theres no way to fix that?

  • grayracer513

Posted April 14, 2016 - 11:40 AM

#10

Yes, there is.  Pump timing and the BK mod.



  • Mr426f

Posted April 17, 2016 - 10:19 AM

#11

How do i adjust pump timing ? And any info or links to BK mod

  • grayracer513

Posted April 17, 2016 - 12:54 PM

#12

BK mod:  http://motoman393.th.../tech/carb.html

 

See the picture for the basic timing procedure.  The idea is to get to the point where the squirt just misses hitting the slide as the throttle opens. 

 

Attached Thumbnails

  • timing.png


  • Mr426f

Posted April 17, 2016 - 04:22 PM

#13

Only thing i dont understand is the screw to cam





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