Do ATV's count? I grew up riding an ever more powerful series of motocross bikes in the 70's. When I was 15, I slammed one about 6' up the backside of a concrete block concession stand after leaving the track boundary. Race days were over because neither the sponsors nor my mother would give me another bike. I've never been back on one. I never rode a street bike. What fun is that? The roads are all flat and you can get ticket if you ride a wheelie or get airborne.
For the past 5 years, I've been riding my brother-in-law's Suzuki ATV. 600cc, 4 speed, about 50MPH top end. Heavily modified suspension, tires, exhaust and clutch. I spend a week at his place in bumble every year and put about 100 miles on some very rough terrain, never flat or straight. I am currently sporting a bruised elbow, bruised ribs on the right, and a purple bruise about 6" in diameter on my right thigh just under my hip. I dumped the clutch a little too early sliding around a turn in a dry creekbed and the quad tried to climb a tree. It did a barrel roll and landed upside-down about 10 feet farther down the creek. I ejected at a 90 degree angle and hit the side of the creekbed from my helmet to my knee. I was the most fun I've had since last year's ride. Always wear helmet, goggles, torso protector, padded riding shirt, long pants, boots and riding gloves. Luckily, I'm too old for my mother to take it away from me and my brother-in-law's motto on off-road riding is, "If you ain't wreckin', you ain't really ridin'!"
Because that helmet was too loose! 
