sandman3577...ok, here's what you need to know about the original belt for the '03 models: Gates manufactured the original belt which weren't the best, then Goodrich began making them, a much better belt over the original. belts are 155 tooth with an 11mm pitch using a rear sprocket of 72 teeth and transmission sprocket of 30 teeth.
now you're going to hear crap like upgrade to the '04 set up or install a chain set up cause the '03 set up sucked or whatever. what people seem to forget is the fact that the '03 model was the first run of the XB line and just like the automotive industry, the next year yields refinements/changes over the previous year model. if it weren't for the '03 models, the others wouldn't have followed with changes. ever heard of improvements, well the '04 model, the '05 model, etc...
there's nothing wrong with the '03 set up as it is, except the original Gates belt. new belt by Goodrich, P/N: G0500.02A8R. I ran my original belt for 66,600 miles with no issues and past the belt onto another forum member that needed one. only changed the belt due to age and mileage and figured it was time.
my belief with why people have or had issues with the belt breaking was by several factors, but not limited to these: environment, maintenance, and how they rode the bike. these are machines like anything else, if you don't maintain them and or do abuse them, sooner or later something will give.
believe me, believe me not, but 9 years of riding the same bike from 2500 miles on the clock to now less than 40 miles from rolling 70k, just saying.