Here are some things you might want to carry:

Good suggestion from Darryl Petrack:  Items to take suggestions:  not really items to take
as such, but packing suggestions:   Be sure to pack tools in an accessible location, esp. if they may be needed for access to cargo -- like the screwdriver I borrowed so many times from Dave because mine was BURIED!
       DO NOT PACK FULL!  One can pack so much better at home with lots of time, but on the road, packing may not be done as well, and overflow becomes a problem.  Also, you may accumulate things (souvenirs, if nothing else) and then you will need a "bag stretcher" which does not work on hard bags!

On my first three trips, I used a large plastic file storage box that had a lip all around the upper edge (which allowed me to use bungee cords to put an ice chest on top of that) and put that on my passenger seat.  That is a huge storage area and is waterproof.  You may want to consider a Givi case ... the kind that has a quick disconnect and you can carry it into the motel like luggage. 

I plan to bring a large ice chest so you may want to get a quart leakproof tupperware container for your snack foods.

Cup holder for your drink

MOSQUITO REPELLANT!  There will be some areas where we need to stop for road construction and the mosquitoes up North are huge!   Make sure you check Consumers Report to get the ones that work.  I like Off!  Deep Woods kind.

Passport and Canada insurance card (your insurance company should give this to you for free)

An electrical outlet so you can plug in a electric coffee mug (Bed, Bath and Beyond has a thermostat one for $19.95 and you can dump in a can of soup and have it hot and ready to sip in a few minutes).

Lip chap

Sun screen and skin lotion

Lightweight nylon long sleeve windbreaker (to keep the sun off your arms and neck)

Sleeping bag (take turns on the floor in motels)

Spare chain; TWO spare master links; Spare tubes, front and rear, Set of spark plugs, air pump to fill tires repaired with tubes above, tire irons or items to serve as such, for changing tires.  (one biker didn't have a spare link and fell behind two days!)

Throttle adaptor so you can keep throttle open with the heel of your palm (or a throttle lock)

Sun glasses 

Powdered laundry detergent and dryer softener (suggest laundry every 3 days)

Rain clothes!  Waterproof shoes or boots.

I found that a couple of jump suits was all I really needed.  These breathable cotton suits block the sun from the legs and arms.  With laundry every three days, you don't need to take along so many clothes.  In fact, pack lighter than you think you need and you can always stop at a Wal-Mart and get more if needed.

Gloves

List of motorcycle service at every location we stop.

A warm jacket (weather unpredictable ... in July 2004, it was 40 degrees all the way across Quebec!)  And then it was 95 degrees at the Arctic Circle!

Please email me at DrASL@aol.com if you have other suggestions.