Small Engine Troubleshooting Problems? Ask a Mechanic Now.
The most likely cause of the clicking sound is a bad battery. The battery may show fully charged with respect to voltage but most likely does not have enough reserve capacity under load of the starter to turn the engine. Try removing the battery and take it to the nearest auto parts store and have the battery load tested to determine if it needs replacement.
The most likely problem is old fuel varnish is clogging the fuel passages inside the carburetor. You can try spraying a brief shot of starting fluid in the air intake. If the engine starts momentarily until it consumes all of the starting fluid then you have confirmed that it is a fuel delivery problem.
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