my 79' xs250 is running really badly at the moment... i rode it home with the knowledge that i should have refueled, but i didn't. now... towards the end of the journey, the bike started doing what its doing now... kind of sounds likes its misfiring (this is whilst moving) i change the fuel to reserve and it keeps doing this so i leave it on reserve and just struggle home (along the highway at 40kmh (usually 100) it gets into my street and dies due to no fuel, i push it the last 20m. go inside and forget about, refuel it the next day expecting it to run a dream, its not any ideas? in short;bike got low on fuel, started running like shit,ran out completely just before my house, refueled once home, still is running like shit; symptons; hard to start idles like shit misfiring (i think thats what its called (irregular sound when moving) won't go over 40kmh/ won't rev over 6,000rpm. my assumption is air just got somewhere it shouldn't have... but yeah... any ideas?