The tack is a Stihl tool that chain saw dealers use to adjust saws and blowers.

In answer to the 4-stroke question: I have also used the tack to check the governor on my Toro mower.

About a week ago I looped the pick up over the plug wire on a model engine and made 4 prop changes for each engine change. Never disconnecting anything while testing for two hours.

Somewhere I have seen similar inductive tacks for lawnmowers and farm tractors in the $35 to $40 price range. I am looking for the source now.

Bill