Fred,
I am going to assume that you red line your engine at 12000 rpm, so that means that it needs 82 cu. inches x 6000=492000 cu. inches of air per minute is required if you engine is at 100% volumetric eff. (Note: the 6000 comes from air is sucked into the engine every other revolution) 220 mph = 232,320 inches per minute. (220x5280x12/60). So now we have the cubic inches of air your engine needs per minute and we have the air velocity in inches per minute so if we divide the cubic inches/minute by the inches/minute we will come up with the the area of the required inlet; 492,000/232320=2.12 sq inches. Going with my rule of thumb of needing the inlet 15-20% larger this would be: 2.12x1.2=2.55 sq inches. If the inlet is going to be round then the diameter is: 2x the square root of (2.55/3.14169)
which is:1.80 inches diameter. Several things to remember here, this diameter is correct at 220 mph so it may actually (and probably will be) a restriction to your engine at speeds below 220 and if you are running a naked or partially stream lined motorcycle going with this small of an inlet may actually slow you down because it will restrict the engine until 220 mph and the aero advantage may not even be seen by a motor cylce that is not fully streamlined. Also this inlet diameter must not have any length to it, you must start expanding the inlet channel immediately after the inlet, the larger the crossection of the inlet the slower the air velocity and the more pressure recovery you will have. The inlet must also have a very generous radius at its leading edge, no sharp edge. My guess is that you are probably running a Hayabusa and if you are running the standard air inlet and air box they are actually quite good. You may see some marginal increase in power if you reduced the area of the two inlets but it may not be measurable.
Rex