After having my XR for a few years I'll start this one off...
Any new XR should have the following done.
1) check and adjust valves
2) detail strip and clean the carb thoroughly. Ensure all jets are clean, ALL passages clear. Measure float level, adjust if necessary. Record all jet and needle settings.
Once the above had been done report back and we can talk. It's a big crap shoot until the above is done.
Best of luck