Right after a ride the engine is very hot. That heat transfers to the fuel tank and fuel, and the hot fuel expands and increases pressure in the tank. When that pressure exceeds the "blow-off" pressure setting in the fuel cap vent system, the vapors are vented. On a California bike, or any car, those vapors go to a carbon canister and are eventually released back into the intake system when the engine is running again. On a 49 state Harley those vapors are just vented to atmosphere. Thus the fuel odor in the garage. This tends to be worse with a full tank. If it bothers you, or if you have electrical appliances in your garage that could ignite fuel vapors, you might want to let the bike sit outside for awhile after a ride, or at least leave the garage door open.
Jerry