Hercules Prima M 5 65 cc airsal tuning, which spark plug? Change the fuel mixture? Change the gear ratio?

Hello, I have a 65cc Airsal engine installed on my Hercules moped with a 12mm Bing replica carburetor. The acceleration was so extreme that the front wheel lifted when starting off with the original gear ratio, so I changed the gear ratio to 11:37. It runs at about 45 km/h, still has a P2 manifold…