Yes, you can ride without your gas cap, but it definitely is a messy endeavor. Depending on your fuel level, gas will splash out of your motorcycle gas tank when you hit a bump. This combined with the wind will translate to you wearing most of the fuel that comes out of the tank. We highly advise against smoking if you have to travel without a gas cap for obvious reasons. When in a pinch, stuff a rag in the filler hole of your gas tank until you can get off the road and locate a new (or retrieve your lost) gas cap.