yz450 08 carb wire mod

5 replies to this topic
  • Windseeker

Posted March 04, 2008 - 04:02 AM


as the Yoshi pipe arrived today decided to do the Redbeard Keihin carb wire mod....
first the New Pipe vs the old one...


looking guuuuud!!! :ride:

then I opened the bowl and got the diaphragm out. The metal tip was already of the required height - 2,5 mm. No mod needed! :thumbsup:


(sorry the images are not quite good)

then I opened the throttle body thing to find and destroy the gap thing. and guess what? no gap at WOT! (second pic) :eek: the throttle stop was just slightly preventing opening it fully so i turned it out probably 3 threads...



which left me a bit happy :lol: and just a tad bit worried :D - is my new bike that perfect(carb wise at least)? or am I terribly mistaken here!?! :ride:

btw - gettig subframe and shock away to get to the carb was quite easy even for me who was doing it - i think - first time in my life! :ride:

so the new bike is slowly getting there :ride:


  • Windseeker

Posted March 04, 2008 - 04:05 AM


oops - i guess the pics loading thing wouldn't work for me today :thumbsup: sorry - will try again...

  • todds924

Posted March 04, 2008 - 06:03 PM


Looking good! I think the 08 carbs are really very good in stock form. I got my 08 dialed in really good using a Pro circuit Ti-4 pipe and only changing the leak jet to a 50 and the main to a 162. I was given one of those R and D powerbowls to try but i'm so happy with it the way it is i'm afraid to change it.

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  • Windseeker

Posted March 04, 2008 - 06:37 PM


yeah - got the same feeling re the RD float bowl thing right now:)
Glad to hear you re happy bout your carb too :thumbsup:

  • 800xr

Posted March 05, 2008 - 07:00 AM


My 07 450 didn't need the AP mod either, but my 06 did have a gap and the carbs are exactly the same. wonder why that is?

  • grayracer513

Posted March 05, 2008 - 07:42 AM


It's because the carbs are not exactly the same. If a gap opens up in the linkage at full throttle, it is because the button on the accelerator pump diaphragm, which is used to limit the travel of the diaphragm, and thereby the volume and duration of the stroke, has bottomed out. It is designed to do this, and that's why there is a spring driving the pump. With the spring, the pump rod can hit bottom before WOT without stopping the throttle from opening farther.

The '07 and '08 apparently have shorter diaphragm buttons. The '08 also has a stiffer AP linkage spring, which more or less eliminates the need to wire the linkage or use an O-ring on it. Merge Racing sells stiffer springs to use on earlier models.

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