less than #42 pilot ?

4 replies to this topic
  • dicko450

Posted January 24, 2013 - 08:21 PM


Hi guys, I'm tuning the pilot jet on my 08 WR450 and I'm currently down to a #42 and it still won't die when I turn the fuel screw all the way in. Is anyone running less than a #42 pilot, from what I've seen #45 to #48 is the norm ?
I pulled the fuel screw out and an o-ring has perished on it but it's the one on the bottom near the knob end so I'm thinking that shouldn't affect it ?
Float height has been set to spec from manual, any clues ? Thanks.

  • MANIAC998

Posted January 25, 2013 - 04:22 AM


There should be only one rubber o-ring on the air/fuel screw. And yes, if it's damaged, it will affect performance.

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  • dicko450

Posted January 25, 2013 - 06:33 AM


This is an aftermarket fuel screw that has two o-rings, one in the usual place above the spring and another one ( the one that has cracked ) at the other end ( closer to the adjusting knob ) which I think is just there to stop vibration of the fuel screw.
Have you heard of anyone using a pilot jet smaller than #42 ?

Edited by dicko450, January 25, 2013 - 06:35 AM.

  • William1

Posted January 25, 2013 - 11:42 AM


I have heard of people needling a piolt as small as a 38. This is because the after market alloy fuel screw tip is poorly formed or too small, causing the circuit to be too rich, resolved with a smaller than normal pilot. It can also be caused by a float that is too high or a leaking float needle seat (or a few other obscure items).

  • dicko450

Posted January 25, 2013 - 06:04 PM


Okay thanks William, float height has been set so should be okay.
I've got a flex jet fuel screw coming so I'll see if that helps. Thanks for the reply.


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