I had an RM like yours that ran great except for a small issue similar to what your describing on the CR. That small issue had me loop out in the whoops at BaJa and about put me threw the wall at Pro Source.
I Cleaned the carb, replaced the slide spring, cable, thwottle assembly, etc.
Know what it was???
Wait for it......
Small pebble stuck in the inlet of the carb (ran threw the fuel tank, petcock and fuel line and got stuck right before the needle/seat). I was just running out of gas at WFO speeds. Check the entire fuel system, and run an in-line filter.