1994 ninja zx9 running rough

My cuz has a zx9 it is running rough.I haven't seen him on it yet.He says when he starts it it revs fine in neutral but as soon as he hits 1st and lets go of the clutch it moves a but sputters and dies out.Can anyone think of anything to try.thanks ahead

 

Maybe the clutch safety / cut out switch?

 

thanks for the reply.If the clutch safety has a little connector wire next to the clutch lever we unplugged that and bike wouldn't run.Today I went out to my cousins house and gave the bike a look over.We took the tank off and there was a connector not connected on the fuel tank,and 2 other wires taped together.So we connected them not sure what they were.Saw what appears to be a fuel pump with a filter gave the filter a shake.Checked the fueses under the seat put everything together started it up and ran with no problem,shifteted fine and sounded good.Not sure exactly what the problem is.Is it possible the filter clogged while bike was sitting?That is the only thing I can come up with.Bike did idle fine without problem until you stuck it in 1st and tryed to move.