If they are not starting I suggest to take out the spark plug and inspect it - is it soaking wet - then you had flooded the engine - no panic it will evaporate and just give you a smoke show when you get her started next.
If the spark plug is damp but not soaked then I suggest you check if you have a good spark. Hold it firmly against the side of the cylinder and crank over the engine, you should have a bright blue snappy spark, bright enough to be seen in the shadow of the bike. If no spark check connectors on the bike, make sure they are tight, give them a goodly wiggle at the terminals to cut through potential corrosion. Rotate the master switch from hell back and forth a bit to clean its contacts. If there is a weak spark then perhaps it is the bonding strap between the upper engine mount and the external coil, if broken just twist it together again for now, replace it later.
If the plug was bone dry, sparks but bone dry then check the fuel is getting to the carb (petcock on?) might be some crapo on the saran screen in the tank (clear screen by removing the fuel line, attach a 2 feet length of fuel line, with the line held up open the petcock and see if any fuel fills the line, turn to reserve and see if any fuel fills the line, you can gently use some lung power to blow into the line, on both run and reserve setting, that would bubble any crap off the saran filter).
Let folks know on this thread how it is progressing...