rotate the engine CCW, looking at the PTO, and observe the exhaust valve, either through the spark plug hole or by removing the valve cover on the side of the engine. Rectangular cover to the left of the carb. If the engine has ACR, you'll see the exhaust valve lift just slightly as the piston approaches TDC.
Could check the pulley on the starter, but I don't know the dimensions off hand, (Merk might) and the engine could have been changed, so it's no guarantee.
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