Slammer, I had an older (94) xr 600 that I recently went through after sitting for six years. Where I live there is a Co. called Al Bakers XR'S only. I went down to there shop and bought a new flat slide carburetor. They set these up according to any mods and elevation that you will be riding.
Bike has never started so easily (it is kick start) and the power is spot on.
Check out their web site for any parts you may need, or some you didn't know you needed.
Pat.