I have a 2000 CR250 which was stock with 13/51. I went right to a 14/48 combination. Essentially it would be like going up 2 teeth in the front, which is a pretty big jump. The only time I find I need to use the clutch a lot is in tight woods. It's real nice for open roads or I guess dunes in your case. The dunes may require a little more grunt then the hard rocky ground I ride. My stock chain worked fine, but I had to grind down the case guard about 50% where it was closest to the chain.
It isn't quite as snappy as before, but I kind of like. It provides nice smooth power and if you need a hit just grab a gear and clutch it real quick.
I thought stock on the '02s was 13/48? If so you could definitely pull a 14/48 combo. Just a thought. I'm sure I might be off on the stock gearing.
Good luck. :cool: