I have a 5hp kart with some mods done and im having an issue with a flat spot during drag racing. I race a 1/10 mile and when I launch it takes off hard then just looses power but after I get rolling about 15-20mph it takes off like a rocket. I richened the carb which helps but it feels like it has a transition issue at mid rpm. id guess around 2800-3000 its flat then comes in hard to 6200rpm. my carb is stock with the twist removed. is there any way to improve this issue by drilling the jet? if so what size? it seems to idle rich and if I richen it more it doesn't like to idle and dies.