Mechanical thermostat in Air-cooled VW

Most of the case, we didn't discuss about the existence of Thermostat at all even in the foreign air-cooled category. Though old Beetle's motor is so designed that cooling system is not liquid cooling but air-cooled, the parts, thermostat is equipped is equipped on the #2 cylinder fin. This mechanical construction controls air amount at first idle stage from closed to fully opened. As a matter for regret, this air controlling doors are kept fully opened because of thermostat failure leading to over cooled condition at first idle stage. This is why make it difficult to keep idle motor control. Most of air-cooled have some failed thermostat that is relatively fail, in addition, this parts never appear in the market, so grasp it without hesitation if you come across wherever and whenever it might be.
Consequently, idle speed control is not always depended only on the construction of choke controlling system installed in the carburetor body, this mechanism is controlled by coiled bi-metal heating electrically. I make it a rule to cut the circuitry at the beginning of first idle while cold season to extend warming up stage.
What I wanna say here is next stage to know the relation with idling stop tendency between BTDC 5 degree and TDC zero. As for my fortune telling, first idle will turn worse because choke control is done under advanced combustion condition. More investigation would be required on this point. This marvelous mechanical controlling system was invented by the German engineers over 50 years ago, interesting don't you think?