Low rpm bog/fuel screw help

4 replies to this topic
  • Kyle_T

Posted July 01, 2016 - 01:55 PM


Trying to dial in my idle and get rid of a slight low rpm bog. 2003 wr450f. Full fmf exhaust and twinair air filter. I dropped down to a 45 pilot jet and it seems most of my low rpm bog is gone.

But what I don't get is I can screw in my fuel screw all the way and it doesn't kill the bike. How can the stock size 45 pilot jet still be too rich even with the exhaust and filter?

When I bottom out the fuel screw the rpm just raises. I've got from a size 50 pilot to a 48 and now I'm down to the stock 45. No matter what I can tighten the fuel screw all the way and the rpm just increases.

  • Krannie McKranface

Posted July 04, 2016 - 12:40 PM


You have changed the pilot jet to the correct size.


...but you have ACV compensation on that carb, which makes in nearly impossible to do a proper fuel screw adjustment, and why so many people block it off and go to the YZ specs

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  • Borgschulze

Posted July 04, 2016 - 01:27 PM


Don't forget to buy a 100 Main Air Jet when you block off the ACV!


Thanks again for the help KRANNIE.

  • Krannie McKranface

Posted July 04, 2016 - 05:17 PM


....oh and the fuel screw should be brass, not alloy....because the alloy one have a taper to them.....and the fuel screw affect nearly only the idle, and has not bearing on bog.


That's the Apump.

  • Kyle_T

Posted July 06, 2016 - 06:49 PM


Thanks for the help guys I'll look into the ACV compensation


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