September 9th, 2010 | 
Author: what is the purpose of choke in portable home Generators & motorbikes ?
What happens when choke is open & when choke is closed ? (what it does to the engine whether mechanicall or electrically, when the choke is open or when the choke is between closed and open marks ?)
thanks in advance
An engine that is stone cold has different fuel needs. It is easier to start one in the fuel/air mix is changed so that there is a lot more fuel int he air (called a ‘rich’ mix) but once the engine gets going, this rich mix causes all sorts of problems such as backfiring, soot buildup and just wasting fuel. You’ll notice that a lot less power is produced when the choke is engaged ("out"). So once operating temperature is reached, the less-rich or ‘leaner’ fuel ration is restored by opening the choke valve.
In most old style carburettors, the choke is a simple butterfly valve (with cutouts) that holds back (‘chokes’) the normal flow of air. (it still lets through enough to pull the fuel up through the jet) There are simpler types (http://static.howstuffworks.com/mpeg/chainsaw0.mpg ) and more complex ways such as altering the main jet level. With direct injection, it is a simple matter of adjusting the fuel flow rather than the air flow.
Posted in Generators
the choke is closed to start a engine this gives a rich mixture of fuel and air as the engine warms up the choke is opened to give a leaner mixture and the choke is off when running temperature is reached if it was still on the engine would cut out because too much fuel
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wx mechanic
the choke restricts the air intake to the engine increasing the fuel intake to ease starting
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When the choke is opened it decreases the air supply to the carburettor and thereby increasing the fuel supply to the engine. This helps overcome starting problem in engine. Once the choke is closed Fuel to air ratio is brought back to its original ratio.
References :
An engine that is stone cold has different fuel needs. It is easier to start one in the fuel/air mix is changed so that there is a lot more fuel int he air (called a ‘rich’ mix) but once the engine gets going, this rich mix causes all sorts of problems such as backfiring, soot buildup and just wasting fuel. You’ll notice that a lot less power is produced when the choke is engaged ("out"). So once operating temperature is reached, the less-rich or ‘leaner’ fuel ration is restored by opening the choke valve.
In most old style carburettors, the choke is a simple butterfly valve (with cutouts) that holds back (‘chokes’) the normal flow of air. (it still lets through enough to pull the fuel up through the jet) There are simpler types (http://static.howstuffworks.com/mpeg/chainsaw0.mpg ) and more complex ways such as altering the main jet level. With direct injection, it is a simple matter of adjusting the fuel flow rather than the air flow.
References :