Idling really rich can drive around but backfires about 1/2 throttle or more. Ran with the air box off can get to about 3/4 then backfiring bad. Have new cylinder head, new valves etc. They are set at.003 for the intake and.005 for the exhaust. DG exhaust i modified the airbox trying to get more free flow by drilling 1/4 holes in the top part at the back of the airbox under the seat. 10 holes. Have a mikuni carb jetting is 45 pilot and 140 main. After warm idles poorly and will stall out unless I turn the idle screw up pretty high in my opinion. I can turn the fuel mixture screw all the way in though and it still runs. So I have a jet kit and rebuild kit in the way. Going to clean the xarb again and let it soak in some cleaner over night but I'm at a loss and have more than I'd like invested into this thing. Any help is appreciated...