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Advise with 2004 DRZ400E Mikuni Carb

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I recently bought a 2004 DRZ400E with the Mikuni carb and immediately had problems, first it leaked fuel when shut off and wouldn't idle so I cleaned the carb and replaced the float valve.  This solved the fuel leak problem however it’s still hard starting under electric start (downhill starts fine with throttle when warm).  So I pulled the carb and cleaned again thinking I missed something, and I did!  I am missing the fuel air mixture screw on the bottom of the carb.  There is a gaping hole where most have a brass cover plate, so I’m unable to adjust/fix the mixture, so my questions are.  


Aside from mechanical error, is there a reason to remove and not replace the air mix screw?


Do I have potential damage from running without the screw in place? 



I see a 2.5-3 turn back-out from snug for stock jets is recommended, are there any noticeable benefits/drawbacks from that?


Note: I have a Yoshimura Off-road RS-3 exhaust and was told the carb was re-jetted, however I cannot see any markings on the jets (old eyes I guess).  Are there any recommendations for jets with that exhaust?  I live in Washington and rarely go above 4000’ above sea level, I just need a reliable starting motorcycle.  Any advice is appreciated!




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When you say the a/f screw is missing you mean it was removed completely and never put back it?As far as jetting goes it'll say the sizes on the jets you just might need a magnifying glass to see them.Honestly at your elevation you may run ok with a few tweaks to stock jetting but its hard to tell until you findout what you have and fix your a/f screw issue.

Edited by minimadness047
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