I've never dealt with the main jet sizes on a Mikuni flatslide. Just the carb on my 1993 XR638 wtih K/N filter, supertrap pipe, extra cooling fins welded on cylinder head. The bike doesn't seem to be very strong up top or through the mid getting there, kinda gets weaker once past 1/3 throttle. Changed plug and it was black with soot. could be from it being flooded so many times throughout the years by previous owner. New bike to me last week. Main jet right now is a 240. 3-4k feet eleveation is generally riding area with temps from 80-90 degrees on average. What can you recommend on the main to get me closer to the ballpark?