What is the reason for the frustration of the newly bought Dayang Taishan 125 scooter after loosening the throttle?

First, check whether the idle speed is too low, whether the mixing ratio of carburetor is correct, whether the air filter element is blocked and whether the spark plug is in good condition. If these are all normal, try to thicken the mixture slightly. If not, you can open the upper cover of the carburetor, remove the vacuum membrane throttle valve assembly, remove the oil needle, add a thin gasket under the oil needle, and try to raise the oil needle slightly, which will generally improve.