If there is a LOT of air bubbles in yer fuel line - it could be a sign of engine vibration frothing the fuel...
But, as Draken mentioned, we need a bit more detail to help ya
So - it'll start and run fine, then conk out on ya? Does it recover? How long does it take to sort itself out? How long can you ride/what speeds before there's a problem?
I know it's so obvious it's silly - but have you gone over your engine to make sure everything is proper? Nothings loosened up on ya?