With the plug out rotate the engine until the exhaust valve starts to open then back up a quarter turn. The piston will now be in the middle of the power stroke.

Off the top of my head i don't remember the specs, .002" to .012" sticks in my mind. In any cae, these engine like being set to the smaller end of the specs.

You will need to modify the feeler guage you use unless using a wire guage. The standard flat blade guage will need a flip the bird finger cut out, about 1/8" wide to work. There is a built in guide between the rocker and cam contact points that will not allow anything much wider to be inserted.

A STIHL dealer was nice enough to sell me a Valve Setting Kit that contained a special feeler gage with a narrow tip, a valve cover gasket, and a small washer. There are no instructions with the kit. The kit was part number 4282 007 1001 A. I did not open the sealed plastic bag with these parts. I will wait until I need to use it. I have not tried to measure the thickness of the gage because it is still sealed in the bag. I thought I read somewhere it should be .010". I wonder if all the STIHL 4-Mix engines have the same valve clearence. Does anyone know for sure? I also have a KM110R STIHL Power head with a 4-Mix engine. However, I put much less time on that than I do on my BR600. Thanks for your interest and comments. Charles Ranheim