I ride a motorcycle now and its a blast. He MUST be safe at ALL TIMES though. Please make him wear a full faced helmet. They make them with vents so they are not hot or uncomfortable. They look great with sport bikes too. Also body armor is a must! with good gloves. Every week i read in the paper about people dying in motorcycle accidents, because they arn't wearing their gear.
I probably would have been messed up if I didn't wear my full face helmet. I wasn't wearing good gloves and just wore a leather jacket when I wrecked. I broke my hand and cut my side. If I wasn't wearing the full face helmet, i would have probably killed myself, or at least tore my face off in the gravel. They make awesome motorcycle clothing (Joe Rocket is a good brand) that will protect all the joints and soft parts of the body. Also highly reccomend the MSF class. Its only 200 bucks (cheaper for kids under 18) and it will teach all the basics of riding and being a motorcycle rider, stuff you can't learn on your own.
I wouldnt' stop riding my bike for anything, I love it. But you have to be safe. It makes me a better driver, plus I save the enviornment :) My bike gets about 60 miles per gallon. I get to pass the cars at stop lights (Lane sharing is legal in CA), get to travel in car pool lanes, first one off the line at lights. Plus I get lots of looks from the girlies!