I look at the port dimensions on these and I can't help but be reminded of old SAAB 36~40 hp 850 cc water pumper triples. Almost the same sort of power to displacement, and from riding my 49cc, they all pull from 2000 rpm up to 5K~6K before they run out of scavenging and start charge contamination 4 stroking. It would be nice if the Chinese makers actually built them with more care and better materials, and true Schnerle transfers and offset the exhaust to the left more.