Motorcycle Repair: Fuel millage, jet needles, psi air

Question
I recently installed a new rear tire on my bike, 1999  1100 Honda shadow Aero... Single crankpin motor. sence then my gas millage has droped from about 45 mpg to 30mpg or less... I have changed spark plugs and that did not help, checked air filter... the only thing I have found is the front tire is wearing a little off centered.. that could be from corning more to one side? it doesn't miss runs strong... I am lost... on what else to try... Thanks for your help  

Answer
Hi Tony,

I need to see the front tire to diagnose the wear pattern.

15 mpg difference is excessive for a tire change alone. If tire pressures are at sidewall recomended psi, air filter and spark plugs are in good condition, I would suspect needle jet wear. Jet needles wear the needle jets in an oval like shape. This is the primary cause for excessive fuel consumption. This occurs gradually and is often not noticed by the owner.

The Aero is a beautiful MC.

Respectfully,
Mark Shively