Hey guys new here, been minibiking since about 82. Currently have a mm80 with 15 street tires. 53 rear 14 front straight chain. 212 w big valve 14cc head 308 cam 20 longer rod ,billet flywheel, straight pipe. I have tried 22mm,24mm flat slide and 28mm carbs.Also had 12 tooth front. Won't turn much over 6000 rpm with me on it, fastest 68mph. What am I missing? Shouldn't it pull more rpm?