Looks like it would have to have a rotary valve with the carb mounted to the crankcase, Suzuki made motorcycles with the carb inside the case with a rotating disc as the valve. How the one in the picture works would be interesting.
Probably a reed valve being front mounted. As I remember the older bikes with the rotary valves had the carb in the case on the engines side. I believe the original Russian engines had the carb case mounted also. Looks like the muffler is on the front also next to the carb? Is the big round object a wheel hub that inserts into the hole in the engines case? Looks like it may have spoke holes? What ever it is its pretty weird.