I have an 08 250r with around 630 miles. Initially I'd get about 35 mph on 6th gear at 4000 rpm and 50 mph at 6000 rpm. Lately it starts off fine but then seems to lose power after riding it for a while and goes down to 30 mph at 4000rpm and 45 mph at 6000rpm. It sounds a little different when it does this and doesn't accelerate as well either. Anyone have any idea why its doing this?