On our trip we left behind the leathers...too bulky to strap on. We had mesh jackets, heated jacket liners and rain gear...was less bulk to strap on.
Octane booster..leave at home...we had no problems with gas out that way.
I carry the extra key with fob in my purse.
Extra qt oil is always good to have...if you travel back roads there isn't always motorcycle oil available.
Sunscreen
With everything we have have to charge at night we have found that carrying a small power strip you are able to plug everything into one place and your chance of leaving one of your charging cords behind is less
trial size shampoo etc..
take a couple less t shirts then you need cuz you are going to buy some on your trip.
Most hotels have a washer and dryer if not the town does.
On our way home we always ship our dirty clothes home and travel lighter. Most HD stores will ship your stuff for you, and you get to buy another t shirt.
HAVE LOTS OF FUN AND TAKE LOTS OF PICTURES