James "Bubba" Stewart has just finished watching videotape of himself launching three stories into the air on a motorcycle.

"I'm a nut, dude," he said after one series of ludicrous jumps. "See, that's a champ," he said another time.

Now, the Tiger Woods of motocross racing is trying to remember when he first met the Tiger Woods of golf, when they hung out on Tiger's practice range and got to be friends, talking about everything except racing and golf and leaping over racial barriers.

Stewart finally decides the meeting took place in the spring of 2003. That would be several months after the teenager became the first black rider to win a major U.S. motorsports series championship, but before the television producers began proposing Bubba-centric reality shows, before Tom Cruise started calling about a movie deal, before the massive Oakley billboards featuring Stewart's face went up in London and Montreal and Toronto.

Whether Stewart has the power to make mainstream what is still something of an insular sport is yet to be determined. In 2003, about 950,000 fans attended outdoor motocross and stadium- or arena-based supercross dirt motorcycle races, which are televised on tape delay and usually draw minimal ratings. By comparison, NASCAR, the country's most popular motorsport, is behind only the NFL in television ratings, with officials often touting a fan base of 75 million.

But while NASCAR is still searching for its first black star -- recently recruiting Magic Johnson to help lead the effort and supporting several grassroots programs for minority youth -- Stewart is already becoming a pop culture icon who could ultimately transform the face of motorsports while broadening the fan base beyond white America.

Since he turned pro in 2002, Teen People has dubbed him one of 20 teens who will change the world. NBC and CBS have featured him on their evening news programs. Hip-hop stars David Banner and Lil' Flip performed at Stewart's 18th birthday party last December, and Stewart rode his bike in the music video for Banner's single, "Crank it Up."

Stewart calls himself "really good friends" with Michael Jordan, who -- like Woods, Cruise, Banner and baseball stars Ken Griffey Jr. and Barry Larkin -- is now on speed dial in Stewart's cell phone. Last month, he landed on Sports Illustrated's list of the 101 most influential minorities in sports, two slots ahead of Magic Johnson.

Professional motocross races are held during the spring and summer on hilly, winding dirt courses in mostly rural areas of the Northeast, Midwest and West Coast. Supercross races, which draw larger crowds, are run during the winter and spring on sculpted dirt courses inside big-city stadiums and arenas. Both feature a variety of jumps and obstacles that take a tremendous toll on the motorcycle riders, who often retire by their mid-20s. Stewart, for example, has already dislocated a knee and shoulder and broken an ankle and collarbone.

The sport's fan base and athletes have long been almost entirely white, and the comparisons to Woods -- which Stewart estimates he has heard upwards of 5,000 times -- were perhaps inevitable.

"It's not simply the fact that he's African American; it's the fact that he's so good at what he does," said Mark Fewell, the senior director of business development for Boost Mobile, a division of Nextel Communications Inc. that sponsors Stewart and several other motocross riders. "He has a huge group of fans who you wouldn't think would normally follow a rider that passionately. . . . If you look at motocross racing, it's not a sport that historically has had a high number of professional athletes from a diverse background; that's just the way it's been. He's certainly blazing new territory."

And Stewart is doing so at a time when motorsports are seeking to diversify both their audiences and their athletes.

Rainbow Sports, a division of Jesse Jackson's Rainbow/PUSH Coalition, began an initiative in 1999 to promote and expand opportunities for minorities in motorsports; last month, the group held a "Salute to Motorsports" at its annual awards luncheon.

After political pundits coined the phrase "NASCAR Dads" to refer to a segment of white, male voters, NASCAR put out a news release earlier this year touting the diversity of its fan base and denying that its followers were a "monolithic bloc" with "homogenous views."

The Drive for Diversity program, which is supported by but not directly operated by NASCAR, this year placed four black drivers and one female in regional racing circuits. Bill Lester, who drives in the Craftsman Truck series, remains the only full-time black driver in NASCAR's top three series.

Observers say the surest way to diversify motorsports is by marketing successful minority racers who, like their white counterparts, have spent their entire lives behind wheels or handlebars.

"And that's why Bubba Stewart is such an important link," said Charles S. Farrell, the director of Rainbow Sports. "It's hopeful things will change, and James Stewart will certainly help things change, just as Tiger Woods brought change to golf with his success and the Williams sisters brought change to their sport. . . . He's proven to be a special athlete, and historically the world has embraced special athletes."

All of which is somewhat amusing to Stewart, who said he'd merely like to be known as "the first James Stewart of motocross/supercross" and isn't exactly sure whether he's trying to change the face of motorsports.

"I mean, I am, but I'm not," he said the day before last weekend's race in upstate New York. "I'm just riding, you know?"

Stewart was introduced to racing by his father, a former local pro in central Florida who gave his son a bike for his fourth birthday. The younger Stewart dominated immediately, winning his first national amateur championship in 1993 at age 7.

Stewart went on to craft the most impressive amateur career in American motocross history, winning 11 national titles. He was featured in racing videos when he was 7, attracted clothing sponsors before leaving elementary school and began assembling his collection of luxury cars when he was 15.

Stewart said that his skin color has never been an issue. "When I came in it I was such a young kid," he said. "I was so small and so young, I never really thought about it. And then once I realized everything -- oh, there's not a lot of 'me' out there -- I was already used to it."

He does, though, have a keen sense of the demands of celebrity, which is one of the reasons longtime fans, riders and sponsors can't stop talking about how their sport has never seen anything like him.

After supercross events, Stewart is famous for charging into the stands or doing victory daces on the podium: The Sprinkler, The Worm, The Bomb. He waves to fans during the first lap of races, a display of showmanship and confidence that has only enhanced his reputation.

Stewart has his own signature move, "The Bubba Scrub," in which he torques his bike nearly parallel and low to the ground as he flies off jumps, at once saving time and thrilling crowds.

No one is sure exactly when or why he became Bubba -- his father speculated that it was a variation on "Boogie," Stewart's other childhood nickname, which close friends still use -- but the name seems to further endear Stewart to his legion of seat-high, Bubba-screaming fans.

Stewart helps design the color schemes for his rack of sometimes outrageous race jerseys, which have ranged from bright pink to zebra-striped and usually feature a red-scripted "Bubbalicious" on the rear end.

And he thinks he'd like to host a talk show and maybe drive for a NASCAR team when he's done with motorcycle racing. Several NASCAR and open wheel racing teams have already approached him, according to Tony Gardea, who became Stewart's full-time business manager three months ago.

"We ride motorcycles and people come to watch us because it's entertaining," Stewart said. "I kind of figure I see a lot of boring personalities out there, and I didn't want to be one of those guys. . . . I keep my part in being a celebrity. You know, it's all entertainment."

Stewart is also tapping markets that have never been a part of motocross, appearing on the syndicated program "Livin' Large" and in advertisements in magazines such as "King" and "Maxim" and "The Source."

Griffey often wears gear made by Fox Racing -- one of Stewart's primary sponsors -- and displays as a trophy the last bike Stewart rode to an amateur title. Rapper and actor Method Man has been spotted in a Fox Racing jersey, and after meeting Stewart this winter, NBA star Steve Francis recently requested Fox Racing shirts.

"What I tell James all the time is he goes from street cred to corporate America without missing a beat, and it's true," Gardea said. "He loves hip hop and rap, that's his music of choice, but he can still go on a billboard for Oakley and sell to a mainstream crowd, still be edgy and not too funky. He has the ability to toe the line between both of those, and somehow, he's kept it together on the track."

Which is something of an understatement. Stewart rides on the 125-cc circuit, considered the entry level of professional motocross and supercross racing, although he'll move up to the higher 250 classification, with its larger, more powerful bikes, in January.

But his results have nevertheless been astounding. Stewart has won 30 of the last 31 heats he's entered, and, barring injury, seems certain to become the most successful 125 rider of all time by the end of the summer.

"He's so dominant, as long as he keeps it on two wheels he wins, there's no getting around that," said 125 rider Kelly Smith, in his eighth year as a professional. "He's going to be an icon for our sport. He's as important to our sport as Dale Earnhardt Jr. is to NASCAR."

Sponsors say much the same thing, which is why Stewart earns somewhere between $3 million and $5 million a year, making him one of the two highest-paid motocross riders, along with 250 star Ricky Carmichael.

Stewart's success has helped his family build a 4,800-square foot home on 80 acres in his home town of Haines City, Fla.; it has paid for Stewart's Cadillac Escalade and Mercedes SL600 and Lamborghini and for the four race tracks on his family's property.

But instead of griping about his wealth, more experienced riders gush about Stewart's potential to infuse their sport with corporate money and a new fan base.

"Every deal he does is the newest, highest deal; he's setting the bar for everyone," said Scott Taylor, the professional motocross team manager for Fox Racing. "If I was a sponsor trying to get into our sport, what do you want to do? You want to sponsor the best guy, the guy who has the best chance to win. Well, hell, it's Bubba."

James "Bubba" Stewart, 18, is being called the Tiger Woods of motocross.James Stewart, left, talks to mechanic Jeremy Albrecht before a practice.