I have a 1990 XR600R that I bought new and a 2000 XR600R that I found in Columbus, Ohio last April and imported to Ontario, Canada. (Another story) Here's a picture of the two biikes in April.
Here's a picture of the 2000 now after a few mods.
I put on an Acerbis 23 litre tank, Renthal bars, 2" Bar Risers, Acerbis hand guards, Stock front fender, flush rear LED signals, XR's Only tail rack, disk guard and chain guard, Wolfman tank bag, fender bag and tail bag, Thumper Racing pegs, and skid plate. It already had the Baja Designs dual sport kit.
Believe it or not, the 1990 is bone stock and has more power especially on the bottom than the 2000 with the Big Gun silencer. The 1990 is also quieter. I'm going to do a little experiment where I switch the entire exhaust systems and carbs on the two bikes. The 1990 has stainless headers that extend all the way to the muffler, but the 2000 headers combine sooner. Will post when done.
I have Pirelli Scorpions for the street and Maxxis Desert IT rear, and Metzeler MCE2 front (not shown) for the dirt.
The 1990 has been well maintained since new but thrashed pretty hard and has never had any motor work other than clutch plates and stator. Even drowned it in a river about 8 years ago but just did 7 oil changes to get the water out. These things are bulletproof.