2006 YZ450F. I'm new to 4 strokes so bear with me. When I hold the throttle steady at about 1/3-1/2 throttle and am cruising in 3rd or 4th gear there is a slight hesitation here and there that almost feels like a miss. When I really lay into the throttle it pulls like a mother and the hesitation is not there. What I'm thinking is that the jetting is off somewhere in the needle, but I'm not sure whether I am rich or lean.