You've got a short somewhere in your electrics, it's usually a live wire hitting off an earth which is then blowing your fuse. The most common short especially on bikes is part of the wiring loom chaffing off the frame. The constant rubbing causes the insulation to wear away & exposes the bare wire. If the wire happens to be live & touches then frame then it shorts out.
It's a bit time consuming on a scoot to find which part of the loom is rubbing where, as you will have to remove some if not all of the plastic panels to trace along the loom to find the fault.
If you find the offending wire & as long as it's not broken or touching any other exposed wire you can simply just tape it up with insulating tape.
Try & tie up or keep the loom away from where it was earthing otherwise you will have the same problem again.
steo, July 2009
