Which is the least likely cause of an engine to hunt and surge at top no-load speeds? a lean air/fuel mixture an incorrect spark plug heat range. a blocked carburetor bowl vent all of the above.

A blocked  carburetor bowl vent

Explanation:

Engine hunt is defined as the continuous  variation in rpm of the engine. It can occur due to various conditions and abnormalities in the inside the fuel injector pump.

In ideal situation, amount of fuel given to the injector is fixed  but in some cases such abnormality arises hence rpm get changed.

Hence of the options available, a blocked carburetor bowl is the least likely cause for engine hunt.

where’s the list ? the question is incomplete

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