unfortunatly, there is no quick fix. What you are probably going to have to do is manualy follow the wiring for that circuit, it may have rubbed through the wire some where. I wish you the best of luck, it's never a fun job.
ok,
try one thing. I have had a couple bikes, and on more than one (cruiser and sportsbike) my wires running down the handle bars have been caught in the "stay" on the tree that prevents the bars from hitting the tank. Once that happens the wires jam together and short the main fuse.