The 2003 AMA Chevy Trucks US Motocross Championship arrives at Glen Helen Raceway this weekend [Sunday 11 May] for the traditional season kick-off, and anticipation is running high as Ricky Carmichael and Chad Reed prepare to carry their Supercross rivalry into the 250cc class.

In addition, the 125 Championship, which many expected to be a cakewalk for defending champ James Stewart, is suddenly wide open after the news that Stewart broke his collarbone in the Las Vegas Dave Coombs 125 Shootout. With the youngster temporarily sidelined, it will give the other 125 riders an opportunity to gain the spotlight and try to get enough of a head start in the championship point standings to keep Stewart at bay upon his return.

Glen Helen, a regular on the series schedule since 1993, presents some of the most unique challenges to riders in the twelve-round AMA Chevy Trucks US Motocross Championship and features one hill - nicknamed Mount St Helens - which is the steepest and most intimidating climb and descent on the tour.

By far the biggest story coming into the opening round is the emergence of Yamaha's 21-year old Australian sensation Chad Reed. The former 125 champ polished off the AMA Supercross season with an impressive six-race winning streak and, even though he came up short in his quest to dethrone Carmichael in the arenas, Reed has certainly established himself as the hottest rider on the circuit. Now he will face the three-time defending AMA 250 Motocross champ in his favourite element - the motocross nationals.

"I think most people know that I'm not as talented in Supercross as I am in motocross," said Carmichael, who became the first rider in AMA Motocross history to go undefeated through the entire 2002 series, "The outdoor nationals come a little more naturally to me and I'm looking forward to the challenge of defending my title."

Reed views the upcoming motocross series as his greatest challenge yet.

"I know Ricky has been dominant in motocross so, if I could beat him in his favourite environment, it would mean a lot," he said, "I'm looking forward to the summer season. I injured my shoulder last year and don't think I truly showed what I was capable of."

Reed added that he still hasn't decided for certain if he will ride Yamaha's new YZ450F four-stroke motocross machine or the proven YZ250 two-stroke he rode during the AMA Supercross season.

"I'm leaning towards the 250 because of the success I've had on it this year," he admitted.

Another big story coming into San Bernardino is the return of most of the factory 250 riders who were recovering from injuries suffered in an especially unforgiving Supercross season. Suzuki will be back to full strength with the return of Travis Pastrana and Sebastien Tortelli, who will join Sean Hamblin in the 250 class. Pastrana is hoping to fulfil the promise in the 250 series he showed earlier in the 125 class, which he won in 2000.

Others on the long list of riders returning from injury include KTM's Grant Langston, Kawasaki's Ezra Lusk, Yamaha's David Vuillemin and Honda's Mike LaRocco and Nate Ramsey. All five are very capable of winning nationals. LaRocco, Tim Ferry and Tortelli join last year's winner Carmichael as former 250 victors at Glen Helen.

Perhaps never in the history of AMA 125 Motocross has a rider been such a heavy pre-season favourite as Kawasaki's James Stewart. The landscape of this year's championship changed dramatically in one fateful moment last Saturday night in Las Vegas when Stewart suffered a hard crash and broke his collarbone. It's not certain when the defending series - and Glen Helen - winner will return, but four to six weeks are typical for that type of injury. That means that Stewart could miss anywhere from three to five rounds of the series.

Also missing from the season opener will be Suzuki ace Branden Jesseman, the 125 East Supercross champ and last year's 125 motocross runner-up, who broke a thumb in practice a few weeks ago and who may only return to action about the same time Stewart does.

It's ironic that the motocross season begins with both 125 AMA Supercross champs sidelined but, with Stewart and Jesseman temporarily out, that suddenly leaves a huge void in the class, which points towards a golden opportunity for the rest of the 125 series competitors. Without Stewart, there is no clear-cut titleist in the series but, perhaps the moniker of pre-season favourite will fall to 2001 champ Mike Brown, another Kawasaki rider who certainly has the credentials to be the frontrunner.

A host of other 125 riders are looking to step up in Stewart's absence. One hot rider in the class coming into Glen Helen is Suzuki's Andrew Short, who won the Dave Coombs 125 Shootout last weekend in Las Vegas, while Stephane Roncada, who was slated to race 250s this year, has been asked by Suzuki to ride in the 125 class at the last minute, making him a big factor. Others to watch for in the 125 class include Yamaha's Ivan Tedesco, Honda's Michael Byrne and Christopher Gosselaar. Exciting additions to the class this year are KTM's Ryan Hughes, returning from retirement and fast newcomer Josh Hansen, son of 1982 AMA Motocross champ Donnie Hansen.