Turn the petcock off, drain the carby, remove the spark plug and kick it with the throttle wide open until your leg hurts.
You need to fix the problem with flooding, the needle and seat will need cleaning/replacing and the float level will need to be set.
Put in a new plug, reverse all other processes and try to start it.
Float level should 20 to 21.5mm on a stock carby.
you want to turn the carb and hold it on a slight angle to measure the float height, like shown here......
it should just barely be touching the inner needle, not depressing it,
here's the float height's of the most popular carbs run on our blasters.......Credit to Awk08
26mm vm mikuni - 20-21.5 mm (stock carb)
28mm vm mikuni - 22mm
30mm mikuni - 23-25mm
32/34/36 tm mikuni - 18mm
30mm oko - 19-20MM.
keihin carbs -
alot of these float heights came from this website, if your mikuni or keihin carb isn't listed above, it will be listed here.......
Allens Performance Mikuni & Keihin Carbs (mikuni)
Allens Performance Mikuni & Keihin Carbs (keihin)
It is possible to check the fuel level by attaching a length of clear plastic tubing to the drain nipple , lifting it up the side of the carby, and cracking the drain screw.
The fuel should show in the pipe to the level of the carb body above the float bowl gasket.