my mates 250 pro 2002 is stuck in first gear so i guess the only thing to do is rebuild the gearbox. Has anyone done this if so any pointers with the do's and don'ts?

Have you tried adjusting the ecentric on the end of the shift shaft yet???????????

My mates 03 280 pro also stuck in first,and we had to do a bit of surgery,splitting the box was simple enough,just the usual make sure you set everything down in order.

There are two small sprung selectors in the selector drum, it was one of these that had broken jamming the bike in first gear,the selector shaft also had a hairline crack and had to be replaced, hope this helps.

Actually I never had the problem myself, or with any that I saw. Seemingly it was down to the eccentric cam affair on the end of the shift drum. Jim Snell in the US had a tech bulletin on it and how to check for it. I'm sure that Kev at GG UK could give you the rundown if necessary. Basically it came down to adjusting the tension and centering of this mechanism. If off, the bike will not shift out of first.

Also verify that the spring on this mechanism has been updated on early 2002 models, as some of the early ones had defective tempering of this spring that lead to it breaking. Updated springs were provided and has a dab of red paint on it to ID it. I'm sure if the bikes been going this long, it's most certainly had the updated spring, so not likely worth worrying about too much.