There will be 60 riders at the start, each one revving his motorcycle engine until it screams. But David Bailey says he will still be able to hear the crowd at RFK Stadium on Saturday. Especially those who have paid to see him crash.

"I don't mind that. I go to see Evel Knievel land on his head too," says Bailey, a 21-year-old professional in one of the newest, high flying, two-wheeled sports that ever landed a rider in traction.

On Saturday, Washington will get its first look at Supercross, a 10-year-old sport that brings the hill climbing, bump bouncing and steep, twisting turns of European motocross into American stadiums.

At RFK, men in tractors and dump trucks are now using 6,000 tons of dirt, 600 hay bales and hundreds of plywood squares to create a fiendishly tough dirt track with ramps six feet high and sand pits 60 feet wide.

The riders, wearing helmets, goggles, mouthpieces, padded pants, plastic chest protectors, leather boots and gloves will push their 250cc cycles over, and occasionally off, the course in a series of races that begin at 3 p.m. Medics will be waiting in the wings.

"I've broken my foot, my wrist, a small bone in my leg, and a hand. I've twisted and sprained a lot of things . . . but I've never been hurt bad," says Bailey, a four-year veteran of the professional circuit from Axton, Va., a town about as small as it sounds.

Bailey won a national amateur motocross championship when he was 16. Earlier this year he won his first professional Supercross event at Anaheim Stadium before a California crowd of 70,000 people. He is very good at his sport, but then he had a bit of a head start over the other dirt bikers his age.

Bailey's father Gary was one of this country's top motocross riders in the late 1960s. From the age of 11, David barnstormed the United States with his father who earned his living conducting motocross clinics.

"We lived in our motor home. I took correspondence courses along the way," says Bailey, whose road life precluded a normal adolescence. "Most people think my father was behind my riding. I had to beg him to let me race."

Bailey says there is good money to be made in Supercross, though he won't say exactly how much. With sponsorship, prize money and endorsements, the top riders' earnings are at least in the six-figure brackets. The best-known of the motocross racers, Bob (Hurricane) Hannah, a three-time Supercross winner, reportedly makes close to $1 million a year.

The sport is not lacking in sponsors.

What the sport does not have and desperately wants is a long-term television contract. Last summer when CBS broadcast a half-hour of Supercross on its Sports Sunday show, the ratings were impressive.

Bailey thinks the sport is ideal for television. Unlike the older motocross where riders disappeared behind hills for minutes at a time, the Supercross audience sees all of the race from stadium seats.

As anxious as Bailey is to please the crowd, he avoids as much of the rough stuff as possible.

"I want to race for a long, long time," says Bailey. "Maybe until I'm 30."