If the float bowls are dry, or there is little fuel in them, the problem most likely lies in the fuel delivery system. If the bike has a vacuum-operated petcock, turn it to prime. If fuel starts to flow, the problem lies in either the petcock or the vacuum line; a little detective work should pinpoint which. If the petcock is manual, move the lever to reserve. If fuel flows, you’re either low on fuel after all, or the petcock main feed is plugged or damaged. If no fuel flows, remove the fuel line at the petcock and try everything again. If fuel flows from the petcock but doesn’t reach the float bowl, the problem is most likely a plugged fuel filter or line.