RE: Can anyone identify this engine?
Dr1:
Some HB engines could be had with Perry Directional Porting (PDP), but they are all still loop scavenged. The PDP is additioinal to the regular system.
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Ed C.:
The HB engines up to the 0.25 used a muffler with a single central screw to hold it on - see the picture I posted of the one in the box. The dark spot on the muffler is the end of the screw.
Bill.