Now, if you really understand how an internal-combustion gasoline engine works, you'll know you're not burning gasoline in the combustion chamber in a liquid state; it's the fuel that vaporizes and mixes with air that ignites. [And before someone tosses the term "vapor lock" into this discussion, let's also understand that "vapor lock" occurs when the fuel turns to a vapor at a point in the fuel system PRIOR to the point at which the fuel system is designed to handle vapor. The fuel lines, pump, and carburetor are designed to handle liquid fuel, not vapor. And "vapor lock" is a sign that your fuel system needs to be running at a cooler temperature.]
Benzene in your winter fuel mix vaporizes easier than gasoline, which makes it easier to combust in the cylinders than cold gasoline that stays in droplets rather than turning to a vapor. And why does a choke work on a cold engine? With a smaller percentage of gasoline turning to a vapor, the choke reduces the amount of air available to mix with that gasoline vapor...and with less air, the vaporized fuel is actually in a more stoichometrically correct mix and more prone to burn properly. The unvaporized fuel is what burns poorly and creates carbon deposits from incomplete combustion. [Google "Reid vapor pressure" for more information than you probably want to know on the subject.]
And as that engine warms up, the fuel system also absorbs some heat from the engine, the cold gasoline enters the combustion chamber a little warmer that it would on initial start-up, meaning the gasoline vaporizes a bit easier. When the engine reaches normal operating temperature, the gasoline should be vaporizing normally and the choke should be completely open.
SO...to answer your Jubilee question...it needs more gasoline in the winter, not only because of the cold air--which IS denser and contains more oxygen--but because less of the gasoline vaporizes properly in a cold engine. "Oxygenated" fuels are used more often in smog-prone areas in warmer weather, when the gasoline blends vaporize much more easily."
To completely kill engine run-on, first do what you can to remove carbon from the cylinder(s). Then when the engine is shut off, make sure the throttle is closing completely so that no additional fuel is entering the combustion chamber. With NO fuel entering to interact with the hot carbon, there should be ZERO "run-on" after the switch is turned off [which either kills current to the coil, or grounds the magneto...depending on your ignition system].
This isn't rocket science. It IS science, but not rocket science. No hoodoo/voodoo/magic is involved...honest.
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Today's Featured Article - Good As New - by Bill Goodwin. In the summer of 1995, my father, Russ Goodwin, and I acquired the 1945 Farmall B that my grandfather used as an overseer on a farm in Waynesboro, Georgia. After my grandfather�s death in 1955, J.P. Rollins, son of the landowner, used the tractor. In the winter 1985, while in his possession the engine block cracked and was unrepairable. He had told my father
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