WR426F Jetting

4 replies to this topic
  • npfman

Posted February 07, 2009 - 06:30 AM


Hi peeps, 1st time poster, long time lurker here :)

I have a 2003 WR426F in supermoto Trim, bought it last november having lots of fun with it, also take it green laning as well, when i can be arsed to change the wheels over.

Anyhoo, took it to my local Dyno today, got good power run 49 Bhp.

Ive attached the printout with the air/fuel ratio, the Dyno Technician reccomends that when the bike is going towards the top of the rev range that it needs to be within the 13 mark, mine is running a little lean in the 14 mark, he reccomended that i go up one stage on my main jet.

Ive taken the main jet out and what looks to be written on it is a K sort of shape and 165S, ive also attached what i found.

Just wondering if anyone can tell me which is the next Jet up and where can i get them from? Im in the UK



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  • byggd

Posted February 07, 2009 - 06:33 AM


Is the 03 a 426 over the pond? Should be a 01-02 with the 450 being born in 03?

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  • npfman

Posted February 07, 2009 - 06:49 AM


Is the 03 a 426 over the pond? Should be a 01-02 with the 450 being born in 03?

Registered from New on a 2003 Plate, could be a 2002 though, just registered late?, Im new to Yams :)

  • npfman

Posted February 07, 2009 - 10:39 AM


The K apparently means its a Kiehin Jet

Going to order a 168 and a 170 Main jet, that sound about right?


Sorry about saying it was a 2003 WR, it was only registered in 2003 :)

  • byggd

Posted February 07, 2009 - 02:45 PM


Yep, 170 would be your next step up. I suggest getting a 175 too in case the 170 doesn't do the trick. Cheap investment!


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