What the List at the top of this threat is missing (besides many other things):
-enlarge inlet port
-enlarge inlet-valve size
-reduce valve shaft size
-optimize valve guide
-re-shape valves
-alternatively change to 4-valve design with according changes to the above
-lighten valve buckets
-improve valve springs for higher revs
-improve exhaust diameter, connections, form and length
-lighten and balance all moving components (crank, pistons, rods, cams if possible, primary drive including clutch hub, alternator)
-coat piston tops (ceramic) and sidewalls (PTFE or similar)
-coat all bearings, cams, cam buckets etc. with DLC (Diamante-like-Carbon)
-optimize gearbox (longer 1st, close ratio gearbox)
to be continued...