Throttle Response

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?

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)

2002 yz426f ?

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.

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.

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

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. 

So theres no way to fix that?

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

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

BK mod:  http://motoman393.thumpertalk.com/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. 

 

timing.png

Only thing i dont understand is the screw to cam

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