poor throttle response top end

i have a 2006 yz250f, adjusted valves and cleaned carb. bike runs poor in the top end range. have changed main from 178 up to 188 and needle in fourth pos. Runs excellent low to mid. Does not pull in 3/4+ throttle.

Could timing be an issue?

any suggestions would help.

why did you change the main up so much? Try backing off some maybe. Somebody will be able to help you out more, maybe try putting it in the jetting section.

started with stock main 178 worked up to 188 to eliminate what i think is a leaning out in the 3/4+ throttle range. did plug test to verify this.

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