Not sure how over filling the tank can make the bike hard starting. Maybe overflows into the evaporative system & back feeds the carb? Anyway take a turkey baster or a tube & pull a pint or two out of gas out of the gas tank. Put the tube deep into the tank & put your thumb on the end, to hold the gas in it, pull it out & drain the gas into something. After getting a couple of pints out of the gas tank, Hold the throttle wide open & crank the engine over for 10 to 15 seconds, or until it starts. If it doesn't start, wait a minute or two to let the starter cool down & repeat. If it doesn't start after three tries pull the plug to see if it's wet. Wet it's flooded try drying the plug with a lighter or replace it. If the plug is dry hold it against a metal part of the engine with the plug wire attached & crank the engine over to check for spark. If you have a strong white spark replace the plug & try starting the bike normally. Hope this helps!
