I've been having a few troubles with my bike lately. After I was hit by a careless driver I went in for a service. The bike was still a bit sluggish afterwards but I got petrol for the first time since the service and she left the Esso garage like a bat out of hell.
I've been told to not let the petrol run completely out as it will drag all the dirt from your tank into your carbs. It turns out us bikes and cars without fuel injection need cleaner fuel, but the millionaire with their fuel injection don't!