I had this on my MS180.
Take the top/rear orange cover off.
You will probably see a loose black wire with an end ferrule crimped on, this earths the coil to stop the motor.
it should be cliped into to the top of the black plastic off/on/choke lever, but the moulded in jaws that form the clip don't hold securely hence it comes adrift.
I've put araldite one mine and it's worked ok for the last year or so.
Rob Laird, September 2009