I just bored out my 1991 cr250 into a cr310 monster. I started richening the slow jet and needle jet 4 sizes richer, and the needle clip is two up. It now has some low end balls, I mean like ripping up the grass and pulling wheelies all through third with a practically bald tire. But now the top end just keeps bogging. Does anyone have any pointers on what I should set my jetting to? Thanks - JAYCE