From the FAQ:
Q: Do I have to carry my own luggage?
A: If you sign up for the Fully-Guided all-inclusive tour, NO. We’ll carry one travel bag for you, a maximum of 50 pounds. You should plan on carrying essentials with you on your motorcycle including water, medicine, etc. All Self-Guided riders have to carry their own luggage and need to be self-sufficient during the day. Some of these riders like to ship replacement clothing and care packages to hotels ahead of time if they have super small luggage capacity on their bikes.