Ty, I can't see from those pictures whether it has a reed valve. I've listened to a couple of Utube videos of them, and they idle implausibly well for a port-controlled engine, so I wouldn't be surprised if they are reed valve. You can work it out from where the intake port is located. If it is very, very low on the cylinder, or directly into the crankcase, it will be reed valve.
We might see pictures that show where the intake port is located, or show the intake system dismantled, at some point.
Meanwhile I've read on the internet that the engine was simply a Komatsu that Briggs marketed for a while (1987-1991). It is unclear whether Briggs actually manufactured or assembled the Komatsu engine themselves for a while during that period. The Briggs code dates Ian's as August 1988.
