Small Engines (Lawn Mowers, etc.): Honda HHR 2165 VKA, auto return, vka

Question
Engine  seems to be running too rich.  Plug is carbon covered. I suspect the choke is not opening . Do you know the theory of operation behind this mower's "auto" choke?

Answer
Most autochoke systems with the exception of the Auto Return Choke System (ARCS) (http://www.jnjhome.net/ope/arcs.htm) use a temperature sensor and an airvane to control the choke.

The sensor is the same sensor used in 70-80 autos, a bi-metal sensor which opens the choke when the bi-metal warms up.  The airvane opens or closes the choke based on the air flow produced by the fins on the engine flywheel.

Can you remove the air filter cover and air filter to observe the choke?

Eric