Reasons for poor gas mileage?

[mr. softie]

Wet weather can have adverse affects if there is a weak spot in the ignition, for example a crack in the insulation of your spark plug wire or "boot", or a myriad of other faults. I like to spray "wire dryer" on all the electrical stuff once in a while to forestall these "leakage" issues. Not that your bike is running poorly because of the wet weather Alan. However too large a spark plug gap(higher resistance) will more likely cause the juice to seek easier paths to ground than a properly gapped plug , and it's worse when components and/or connections are damp or dirty. (Saw the pics of your plug Alan, looked like a bit of erosion/wear on your plug had possibly enlarged the gap out of spec).

Back to the OP's question of why the poor gas mileage, I was doing service to my bike today and noticed the rear brake was not releasing fully, because of a sluggish cable. I had noticed my mileage dropping a bit as well. I disconnected the cable at the wheel, disengaged the clamps, raised the back end of the cable, and funneled some PB Blaster into it. Presto no more sluggish cable and my rear brake is releasing as it should now. So it could just be something simple causing the drop in mileage. Front calipers can also bind and cause a dragging front brake. so if possible raise each wheel off the ground and give it a spin to check.