Has anyone here tried to heli coil a lawnmower sparkplug hole on a small engine (Kohler, Briggs, Honda). Does this work or when you remove the sparkplug does the coil backout?
They work fine, just make sure that the spark plug threads don't extend past the end of the coil, because if carbon can build up in the spark plug threads it will pull the coil out when you remove the plug.
I've do it 5-6 times a season. Make sure the threads are clean and dry before installing. One trick I learned was to add sleeve lock to the helicoil when I install then. After it dries you will have a solid connection.