Mkksat13

I have a Zuma 49cc 2 stroke. Last time riding I was cruising at 40 mph then the speed just dropped to 30-35, out of no where! This happened after about 30 minutes. It never got back up to speed and seems to have just lost top end. I took carb apart & cleaned, new plug, fuel supply/vent okay, air filter okay, exhaust manifold gasket/seal checked, and also burned out the little carbon that was in my exhaust pipe. I am at a complete loss. Would reeds have this effect on scooter after it heats up? One reed was against the valve, and the other 3 had a gap of about 1/8”. Or could it be cylinder/top end damage or wear? Thanks for any advice. I just don’t know what else to do.