where do I attach the threeinch grouding wire for the switch shut off?

As far as i remember the cut out wire came from the coil up to a plastic insert under the back handle, it had a barrel connector on the end which fitted into a slot in the plastic insert, there was another wire opposite to it which also fitted into the other side of the plastic insert, the other end of this wire fitted under the head of one of the carb securing screws to earth, as you pushed the on / off switch a copper plate came down on top off both wires making a join thus earthing out the coil and stopping the saw,

Husqvarna man
December 2009