need more info Pete. Was this the first time you ran it? I’ve stuck two pistons like this (melted down at the exhaust port) and they both were due to severe lean condition due to a leak in the carb boot. I kept running larger and larger jets, but just couldn’t keep up with the leak.
Probably not due to the low end circuit. Bogging when quick off the throttle is usually a rich condition. What the the exhaust pipe (exit) and spark plug look like?