My bike has been sitting since august. I took the bike out two days ago (petcock on reserve) got two blocks and it felt like it ran out of fuel, tried the starter until battery died. got home, thought I ran out of fuel. Next day topped up fuel, charged battery, bike ran fine all afternoon. Today I started riding, got a block, realized petcock was on reserve, sswitched it, made it two blocks, and died. Let the bike sit for an hour, bike started up and ran fine all the way home (petcock in "on" position) and a bunch of laps around the block. I was thinking maybe a blockage for the on position of the petcock, maybe fuel filter, but I just ran it around the block at high rpms...the vacuum line was replaced recently. Any ideas how to determine the problem?