Oil leakage of the carburetor 
Cause: there is foreign matter on the contact surface between the pin valve and its valve seat; the pin valve wears; the floater is damaged or immersed in gasoline.
Eliminating method: clean the carburetor, replace the worn pin valve, pin valve spring or the float. 
 
Starting difficulty 
Cause: The carburetor oil inlet passage or the orifice is blocked; Idle speed is slower; Starting and thickening system is invalid; the starting method is incorrect.
Eliminating method: Clean the carburetor, quicken the idle speed, adjust or replace choke device, and use the correct starting method. 
 
Idle speed is unstable 
Cause: When the oil passage or gas passage of carburetor idle speed system is blocked or leaked, oil supply in the idle speed system is thinner or thicker, which causes that the idle speed of the engine is unstable. 
Eliminating method: Clean carburetor, replace idle speed orifice, replace carburetor’s sealing paper washer, and tighten the connecting bolts and nuts of the carburetor and the air inlet pipe. 
 
Lack of power 
Cause: idle speed orifice or the main orifice is blocked, idle speed oil passage, gas passage or main oil passage or the gas passage is blocked.
Eliminating method: clean the carburetor, replace the worn main orifice and main nozzle and idle speed orifice and so on.