Didn't run out of gas did you?
I know that it is a silly question but you idn't give us much to work with.
Is the bike stock?
What gas oil mix are you running.
Did the engine sieze or just quit running?
Have you cleaned all your fuel filters?
Remove the fuel cap to see if the vent hole is plugged.
Have you been able to get it started again?
What make and model is the bike?