Spring and autumn, between winter snowstorms and the blazing summer sun, are the best times for motorcycle touring in the Grand Canyon area. Watch out for late-summer thunderstorms, which can spout hail and lightning July-mid-September, mostly during the afternoon. Arizona law requires helmets for riders younger than 18 and eye protection for drivers of motorcycles without windshields.
Be visible: Traffic around Grand Canyon Village [1] is heavy, with lots of distractions, and the long, open, straight stretch on Highway 64 from Williams to Grand Canyon is notorious for inattentive drivers. Stick to walking and shuttle buses in the South Rim’s congested village area, and save the bike for Desert View Drive [2]. If you prefer open road, head for the North Rim.
If you like to keep a close watch on your ride, note that Maswik and Yavapai Lodges are most likely to have parking spaces near your room. Mather, Desert View, and the North Rim Campgrounds all allow motorcycles.
Route 66 towns near Grand Canyon, including Williams, Flagstaff, and Kingman, are popular with bikers, and if you need repairs or gear, these are your best bet.
Links:
[1] http://www.moon.com/destinations/grand-canyon/the-south-rim/sights/historic-grand-canyon-village
[2] http://www.moon.com/destinations/grand-canyon/the-south-rim/exploring-the-south-rim/driving-tours