Hesitation Around 4500-5000 RPMS

Put in an adjustable fuel screw(Tusk)and after seating it backed it out 2 full turns,and filled the tank with some VP Small Engine 94 octane fuel(Ethanol free).Started on the 4th kick and took it around the neighborhood for about 10 minutes to get the good gas through the carb and noticed some hesitation around 4500-5000 rpms(bike is a 2007 CRF 450R with 38 hours).Never noticed it before the new fuel screw and and VP gas,anyone have any idea as to what may be causing it?

Thanks guys,


1. Fuel screw is for idle circuit only. Once your turn the throttle 1/16, it's no longer an influence.

2. Jetting is for throttle position, not rpm. Rpm is ignition and scavenging (porting, pipe). 

3. You don't need VP fuel, and if you do use it, you will be LEAN becuse fuel like that has more oxygen molecules in it.

Use pump fuel

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