Merlins? Common as muck! 🙂

I stand corrected on the cylinders.

Notice how the bottom section of the junkhead (where the spark plugs go through) has dropped down into the sleeve slightly; there should only be two ring-grooves on it, and not that gap above them. That bit of the junkhead is only a press-fit into the upper section; it has to stay in place with the sleeve-valve and piston moving up and down at all temperatures and power setting of the engine…

…that’s some class engineering right there!