In answer to your needle clip question, yes, dropping the needle down a clip lowers it into the main jet emulsion tube which narrows as it gets closer to the main jet so lowering the needle blocks it more thus reducing the amount of gas you are feeding the motor.
Alternately raising with richen your mixture.
If the bike has been sitting for some time it may pay to check that the very tiny holes in the emulsion tubes have not become blocked
If it is a gas supply problem as Crashbar said, pop off a pod filter, lift the carb slide with a screwdriver and squirt some starter fluid (which is mainly ether so go easy on it) into the body of the carb, kill switch off, igniton on and hit the button, if it doesn't even burble then there is something else wrong, I wouldn't run it too long like that though as damage may occur.
Just another thought, as you've been playing with the carbs/jets etc check that the slides are not actually totally closed at rest.