I have been looking for a shock upgrade for the xr for half a year. Mine is a 2002 which has a shitty non rebuildable shock. The early 84-91 models have rebuildable tunable shock but rarely come up on ebay. I found a top of the line WORKS shock on ebay for an 1/8th of the price. when I got it, it needed a new bladder, valve, and adjustment rings but Works was able to sell me all new parts and I rebuilt it.
The bike is now way better and doesn't bottom out.
I also replaced the steel swingarm linkage with aluminum linkage to save weight and a longer wishbone to lower the back end to better match the small 17" front wheel.