by bluemower » Mon Dec 04, 2017 10:49 pm
usually, the auto choke engines are very easy to start when cold. On Briggs, this is due to a high output ignition system and a smaller venture in the carburetor. When the engine starts, air from the fly wheel pushes against an air vane and opens the choke. A problem occurs when the engine is started and operated for about one minute - then shutoff. When an attempt is made to restart the engine 30 seconds later, the engine will not start due to flooding. In this situation, the Thermostat has not warmed up and makes no effort to partially open the choke. The choke is still spring loaded close - but the engine no longer needs full choke.
Briggs issued a service bulletin that instructs to eliminate any space between the thermostat arm and the air vane that opens the choke. This adjustment works ok at sea level. At higher altitudes, the Briggs adjustment may not solve the problem. At 7,200 feet, I install the high altitude jet and instruct owners to keep the cold engine running for at least 4 minutes.
On Hondas with the "clock" mechanism choke, this system has a problem sticking. On high altitude engines, allow the choke to open about 50 % - before pulling the rope. Later Honda auto choke systems continue to have problem just like the briggs.