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Mr426f

Throttle Response

13 posts in this topic

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?

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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)

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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.

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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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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. 

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