Motorcycle racer Kenny Roberts was burning rubber at 170 mph when a tire blew in 1976, but, mercifully, it cost him only the race. In 1978, testing tires in Sweden, he went over the handlebars at 80 mph and incurred a concussion; that sidelined him 24 hours. Then, last February, while shaking down a new bike in Japan, Roberts slammed into a retaining wall at 100 mph; this time the damages were two compressed vertebrae, a ruptured spleen, a fractured ankle and blocked intestines. "The doctors said there was no way an average person could be up and around so quickly, let alone almost completely recovered," crows Kenny. He was back in competition in two months.

Roberts, now 27, didn't just recover. Though he missed one race on the circuit, he enters the French Grand Prix Labor Day weekend having all but clinched his second straight world title. No American has won even once.

He has only one racing style: flat out, trying to fuse his body into his four-cylinder, 500-cc Yamaha as the slipstream tears at his helmet and at times he nears 180 mph. Others may pull into the pit when a tire frays, but not Roberts. "When the rubber gets hot and thin enough, it's like riding with grease balls on the tire," he says. "A lot of fast riders are really spooked."

Roberts isn't. "At 180," he says, "when your front wheel wants to play pogo stick, you don't do nothing. You don't sneeze, you don't hiccup, you don't even breathe. You point it and hang on."

Kenny recalls the first minibike he straddled when he was 12 back in Modesto, Calif.:"I almost crashed twice, but I thought, 'Man, this thing goes!' " Roberts cannibalized a bicycle and a power mower and built his own five-mph motorcycle. By the time he was 14, he rode a 50-cc machine in his first race. The bike died on him. Roberts got off and kicked it.

After four years of amateur racing, Kenny quit high school to turn pro ("I was good at PE and that was about it—I cheated just enough to pass"). At 18, he took the American Motorcycle Association's novice championship. At 21, he became the youngest U.S. grand national champ in history.

Last year Roberts faced a choice: to leave the American tour, because his Yamaha bike was no longer competitive on dirt tracks, or end his lucrative affiliation with the firm. He left the U.S. and won the world championship his first time around, racing on such devilish European tracks as Germany's Nurburgring (where 172 turns are compacted into a terrifying 14.7 miles). He also became a leader among the drivers, staging a boycott of the Belgian Grand Prix this year when the track was poorly resurfaced.

His success will bring Roberts more than $700,000 in prizes and endorsements in 1979. It also allows him to employ his now divorced parents. His ex-laborer dad runs a racing equipment shop; his mom, who ran a Modesto grocery, manages a small apartment complex Kenny owns.

His marriage to Patty Rapp is not thriving, however. Last year she, with Kenny Lee, 6, and Kristy, 3, toured with Roberts in a roomy $35,000 motor home. This season Patty stayed in Modesto to take care of their newborn child, Kurtis. When Kenny returned in May, he found she had other interests. He relates, "I told her, if you feel you can find something better, just gas it up." He has found new companions.

Roberts says he understands why Patty got turned off. "It's tough following me around. Even between races when I'm at home, I'm not really there. It takes me a week to slow down enough to eat, watch TV and go to bed in a normal way. It got to her and I couldn't help." But adds Kenny, "You don't stop racing when it's in your blood. I'm used to going, going, going. And I've got to go on."