Sounds like maybe you have the wrong jets/ needles installed. You should be at 40 mpg +. The Dynojet kits have a tendancy to run rich (lower fuel mileage), Maxair kit leans out the engine a bit (better mileage). Gas mileage also depends on how you ride, if the bike is in proper tune, how the bike is loaded, ect. Full throttle from a full stop will kill mileage as will running above 65 mph. Measure your gas mileage over a period of time, writing down mileage, and gallons used at each fill up, then figure it out. You will be surprized how it will change.
I have basicly the same setup on my 1100 and get between 38 and 42mph depending how I am riding.
I am sure someone else will have other comments on this. Just my 2cents worth.
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