Not really. Its always that consistent without much of a headwind.

 

I have a 103 Stage2 with 255 SE cams. I consistently get 38-40 riding 2 up with luggage. I never use 6th gear below 70 because it just seems to lug too much. If I twist the throttle I want to feel it.

 

Low to mid 40s consistently. Occasionally will get 50 mpg. Used to keep spreadsheet and document every drop of fuel and mile ridden but got bored with it.
Stage 1 TC 96 with 50k

 

I use an app on my phone called FuelLog pro. You put your fillups in, but you can also add other costs. I use it to keep track of fuel and oil changes on everything I own. It will give you a break down of how much you spend annually/monthly/per mile/etc. It's easy to use, as long as you remember.

 

I have a stage 4 103 putting out 118 hp and 122 pounds of torque I can get 40 to 42 miles per gallon all day riding two up

 

40-42 mpg, and it pulls 6th gear at 55-60 all day long. no prob.