Eric Rupe, 18, of Tampa, Fla. overcame the mud and the competition to win the $1,500 Pro-Class BMX "War of the Stars" bicycle motocross race yesterday at Starlit track in Fairfax.

For Rupe, the nation's top-ranked pro racer, the victory brought his year's earnings to $9,000. "In pro class," said Rupe, "the race is close all the time. You can never really tell who's going to win."

Before the final, Rupe had easily won his two qualifying heats.

The track conditions were horrible for the scheduled 10 a.m. start of the motocross, a series of more than 220 preliminaries and finals for bikers aged 7 and up. An overnight and early-morning rain left the red dirt course so sloppy that sponsors feared cancellation.

But track officials took shovels, rakes and brooms and cleared away most of the water. Still, the course was so sloppy it had to be shortened by 80 yards.

"That's a good thing too," Rupe said. "Otherwise no one would have had the strength to finish."

"He's right," said runner-up Mark Driscoll, 18, of Cedar Rapids, Iowa. "It was so bad and so slick that you could hardly pedal out there, let alone stand up. It might not look too tough, but the mud takes it out of you. Now if that track had been dry, you'd have seen us blaring."

BMX racing is done on low-slung, high-handlebar, 20-inch bicyles along a twisting, bumpy 10-foot wide track clogged with seven other riders, all of whom will ride over your face if necessary to win.

To be good, a rider has to be daring, aggressive and tough. Even the little ones. In a 7-year-old novice race, a violent collision left two racers lying in a muddy divot on the treacherous third turn. "Get up and run your bike over the line," screamed the father of one of the fallen. The boy slowly rose, grabbed his bike and limped over the finish line before collapsing. Hardly any of the 1,000 spectators raised an eyebrow.

When the medics wanted to cut the pants off his son, who wasn't seriously injured, the father said: "No way; I spent $60 on those."

Which means serious BMX racing is expensive: a minimum of $500 a bike. "Mine ran about $650," said Rupe. "And that's just the beginning of the costs."

Serious racers use serious equipment: $120 helmets, $25 gloves, $60 pants and $20 shirts. "I have a sponsor, so luckily I don't have to pay a thing," Rupe said.

Sponsorship is what most BMX racers strive for. Yesterday, most of the riders were representing the 15 factory teams in attendance. So each race featured a madly pedaling collection of human billboards.

There were no serious injuries, although bicycle motocross can produce many. "It's amazing, but all I've ever gotten was a fat lip," said Rupe. "But I've seen guys get broken legs and arms. Broken collarbones are the most frequent."

"I got a concussion in a St. Louis race last year," said Driscoll. "And a couple of years ago I tore some ligaments."

Though bones stayed intact, egos didn't. Seven-year-old Jason Eiser, the top-ranked Maryland and Pennsylvania racer, got his bike stuck in a foot of mud and couldn't finish the race. He was so shattered he started to cry.

One competitor, after taking a mudbath because his thin-tired bike couldn't grip the sloppy track, decided to give his bike a bath in return. He strode over to the small lake on the side of the track and threw the $600 precision-tooled machine into the water. It was still there an hour later.