Motorcycle failure

Wear of camshaft and rocker arm will not cause runaway, but runaway is generally caused by the position where throttle pipe and throttle cannot be reset or cylinder compression leakage. Although you have checked the carburetor, valve and throttle pipe, I suggest you check again whether there is any leakage in the intake pipe between the valve, carburetor and engine and the suction pipe of the vacuum box switch, and whether the carburetor throttle can not be completely closed. If possible, you'd better try another carburetor. The throttle of some carburetors will not close properly, especially on mopeds.