Pw 50, cleaned air filter,put new plug in,bike starts fine,then feels like choke is on and bogs down,plug is wet ,smells of petrol,,,,no power , tried running to clear through ,sputters then sounds really nice and crisp goes really well but then bogs again...think maybe carb or airscrew needs adjusting? not sure of what compression is hoping not piston rings,,,if it was, would it clear and run finr like it does for period? has a new mikuni carb on it ,fitted by shop,....! tried drilling couple of holes in top of airbox for more air , and has already had restricter washer from exhaust removed. yamaha pw50...