Yup, thankfully these have normal 14mm plug threads, and it's read between 155 and 160 over several tests. Decomp is plugged. Feels good when starting.
I had the cylinder off to check out the piston, which has time on it but the skirt measured ok, and ring gap was still reasonable. Forgot to take photos, but below are port shots.
Thanks for any hints, I'm not an expert with the modern Stihls. This one couldn't be too old, has the newer 100362B Zama. Serial # wasn't registered by whatever dealer sold it, but it wasn't used to cut wood. Never had oil in the tank, dirty with some kind of rock/masonry dust, spike and catcher missing, no sprocket. Coworker inherited it with lots of other half-running equipment from a relative's business in California.
View attachment 205361 View attachment 205362 View attachment 205363