Driving the motorcycle wear:
Helmet
Neck protector or Bandana (protect your neck from cold, from stones or flying insects & your mouth from dust-in hot weather, soak it in water and tie it around your neck)
Motorcycle Jacket - Leather/Cordura/Scuff-resistant material/hard shell protection (Back Protector) - Liner or an Electric Waistcoat in Winter
Motorcycle Trousers - with a hardshell protection or MX trousers and with either in-built waterproofing or a using separate rain suit
Waterproof or with a separate thin breathable Rain Suit/poncho
Comfortable Leather Gloves
Boots - heavy waterproof with foot, ankle & shin protection

Items you need quickly:
Mobile phone with a list of phone numbers of your travelling buddies & recharging cable
Camera, spare battery, film; if digital - recharging cable, enough memory; mini-tripod
Disc lock
Maps & Guides (GPS is handy in towns and back roads BUT only IF area is mapped for GPS)
Sun-block
Chap-stick for lips
Spare spectacles & contact lenses (if required)
First Aid kit
Multitool

Rotate & wash under-clothing - take no more than 3 items of each
3x shirts - long/short sleeved or T-shirts
1 extra long trousers + shorts
Swimming togs
3x Underpants
3x Socks
Walking shoes
Warm long-sleeved sweatshirt
Light shower-proof jacket/poncho
Towel
Laundry detergent (powder) & clothes-pegs (for washing out a shirt in motel room) or use same-day hotel laundry
Hat or cap

Wash Bag containing:
Razor & oil with spare blades (if required)
Soap, liquid in a small plastic bottle
Tooth-brush & Tooth-paste
Hair & body shampoo
Toilet paper
Comb
Pair of Flip-flops (protect the soles of your feet in communal showers)
Sun-block & Insect Repellent - maybe even a mosquito net for sleeping
Chap-stick for lips
Spare spectacles & contact lenses (if required)
First Aid kit
Emergency medical and contact info in wallet, or on an info tag around your neck

Can or tube of Chain spray (if you ride a bike with a chain)
Chain master link
Toolkit
Spare bulbs
Cable-ties
Cleaning rag
Spare dark or light face shield/visor with spare helmet hardware (plastic screws)
Ziplock freezer bags (thousands of uses-you can even drain petrol into a bag from one bike's petcock, then pour it into another bike)
Duct tape and electrical tape (wrap a small amount around each leg of the pliers in your bike's tool kit to save space)
Puncture repair kit (tube or tubeless, depending on your machine)
CO2 cartridge tire inflators, air pump or any type of inflation device
Handi-wipes for cleaning those hands
Flashlight
Multi-tool or Swiss Army knife
Tyre pressure gauge
Extra fuses
Extra ignition key
Water bottle
Earplugs
Spare Gloves - wet & dry
€20 bill hidden on bike
Chain Lock/Cable Lock/U-lock/

Passport (and visas if required)
Driving licence (full not provisional) (Maybe an International Driving Licence if required)
Vehicle Registration Document (original) & Up to-date tax disc/licence plate
Vehicle Insurance Document
Valid Health Insurance, Form E111 (within EU)
Cancellation, Motorcycle Breakdown, Motorway Recovery & Repatriation Insurance
Use a separate wallet for daily purchases & keep your credit/ATM card & main wallet hidden - if you're mugged or stopped by a roadside cop show your daily wallet

Minimum:
Tent (size & quality depend on need - for motorcycle travel choose small packing, light, strong material, poles & pegs)
Peg Hammer
Ground sheet
Sleeping bag (size & quality depend on need - for motorcycle travel choose small & light - I recommend Snugpak)
Air bed/Therma-rest (unless you're camping on soft grass)
Insect Screen in tent (may be built-in)
Insect Repellant Spray
Unbreakable cup and a line with some pegs on which to hang washing

Cooking yourself takes time and adds heavy, sharp & soft luggage - better to breakfast and dine in a nearby diner/cafe & meet local people. For a group traveling together, spread the load among everyone!

Multifuel Stove
Fuel Container
Kettle, frying pan, boiling pot
Cutlery - Knife, fork, spoon pp
Cup, Plate
Water sack
Containers - Salt, Pepper, Washing liquid
Tin opener
Bag for unused cooking ingredients