Over the years most manufacturers have made lots of improvements to Cylinder port shapes.  Most cylinders can actually flow worse, if you grind /polish the area,s from under the cylinder. If you take material away, you may decrease bottom to mid power, as this effects the primary compression ratio. This can be corrected with case stuffing.  Without a good  small Dyno, you may not realise whats happened.  The curves in the transfer ports have now a more tighter curve, increasing the slug volume speed into the cylinder, KTM have pioneered this design which works really well, and yet the ports look small! High air speed is gained. Most surface finnishes on modern cylinders cannot be changed, to gain power. Even the exhaust expansion chamber inlet is now smaller than ever, on late model pipes, keeping air speed high.    However, there is still work that can be done, port windows, chrome rough edges, and the whole exhaust port can be changed that yields good power improvements over most of the rev range.  Cutting through the chrome is tricky, most engine porters now using some lubrication/cooling method, so as the chrome plating is not being effected by heat and vibration.   Dyno testing with many cylinder port shapes, sizes, heights etc is done to make sure the power is gained.  So before you grab that file, or porting tool, call and have a chat, we can hopefully save you some time.