Hi. I have a Piaggio Liberty 50CC 2T 1997. Recently I changed the carb(12mm) with a brand new one of 17.5mm. After that I went to a service and the mechanic blocked my oil pump cause I had some problems with the screw which goes into transmission. He blocked the oil pump to be always opened. I also changed the gas valve and the air filter with a new one. Now often when I go full throttle the engine dies and I don't understand why. Also, if I use throttle just 15-20% it works, but he wants to die. Can you have any ideas which can be the problem?