I think those are the older D-5 or similar motor, with the crankshaft acting as a rotary valve. The piston port China Girls which are the common design now are derived from a later, cheaper manufacture, D-8.
From a series of D motors, D-6 was considered the most successful. On D (D) -5, D-6 engines, the crankshaft was balanced.
Someone managed to sell the D-5 engine to the Chinese, and they began producing their own engine under the brand name F-50, F-80, but not with the spool inlet, but with the usual one through the cylinder.
As can be seen in the photo, the Little D-5 engine is installed on which the ignition and armstarter from the F-50 (80) fit without problems.