Carburetor

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  #1  
Old 03-27-09, 07:34 PM
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Carburetor

Hi,

I am a newbie and wondered if someone could tell me what the Carburetor does and how it works? I know that is does something with air and fuel, but I don't really understand it. Also, on a lot of the posts, folks have to rebuild their Carburetor. In rebuilding, is it really just cleaning the varnish out and installing new gaskets? Is there a way to maintain the Carburetor so it doesnt have to be rebuilt?
Thanks,
Bosque
 
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Old 03-27-09, 09:12 PM
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You hit it pretty much. The purpose of the carburetor is to deliver a fuel-air mixture, in the proper ratio, to the cylinder for combustion. That was a fairly good description of rebuilding one. There are also some parts which are routinely replaced when rebuilidng one such as the float, needle, and seat which are what control the level of fuel in the carburetor bowl (on those applications that have a bowl). Eventually any carburetor will require an overhaul. About the best advice for longest life is to use fresh fuel and always use a fuel stabilizer.

Some good info here:
Carburetor - Wikipedia, the free encyclopedia
 
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Old 03-27-09, 09:14 PM
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Any internal combustion engine needs four things to run. Fuel, air, ignition, and compression and all have to occur in the proper amount at the right time. The carburetor takes care of the fuel and air.
Gasoline does not burn in the liquid state, it needs to be vaporized as in mixed with air. The carburetor does this under varying speed and load conditions to maintain the correct ratio. Under ideal conditions this ratio is approximately 14 parts air to one part fuel.
Modern fuels are made up of a lot of chemical components with a petroleum base. Some of these components break down over a period of time and form other compounds that harden and plug up the passages in the carb. They also cause perishable parts like gaskets and seals to deteriorate.The best maintenance is clean fresh gas with a fuel stabilizer that slows the aging process.
 
  #4  
Old 03-27-09, 09:14 PM
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Just generally speaking it mixes fuel (liquid) with the air at a ratio of around 18:1 (give or take a little). It also provides a starting circuit (choke circuit for cold starting). It roughs in the ideal fuel/air ratio of 18;1 through two primary circuits of the idle jet and the main jet. The circuitry of the main jet has some adjustable metering with an external adjusting needle.

There a number of different designs to carburetors - some have different adjustments you can do on the mixture, but the above gets you the general idea.

As a rule if you keep fresh fuel or at least stabilized fuel in the engine tank/carburetor you shouldn't have a fuel breakdown which results in varnishing of the carburetor. Today's fuel is much worse than some years ago in its short shelf life.

There are some parts in the carburetor like gaskets and "0" rings that have to be replaced periodically as they dry and crack, allowing air or fuel get past the points they are there to seal. That type of rebuilding is to be expected. However if you keep the fuel filter current and clean and take care of the fuel deterioration issues you can keep the carburetor work to a minimum.

TG !!!!!! You won the race on this one.
 
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Old 03-27-09, 09:15 PM
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Great minds think alike!
 
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Old 03-27-09, 09:17 PM
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Great mind ........ mmmmm. I don't think I got one of those yet.
 
  #7  
Old 03-27-09, 09:35 PM
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Thanks guys. That makes perfect sence.
 
  #8  
Old 03-28-09, 06:15 AM
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The reason carbs on small engines (lawn mowers, snowblowers, weed wackers, etc) need to be rebuilt so often is that they are "seasonal use" equipment and are not used everyday like your car. Even lawn mowers only get used every 2-3 weeks. Snowblowers are not used from mid April thru mid November. Many people do not store them correctly. It sits just the way they left it after they used it last with gas in the tank. Today's gas is good for only 30 days. And with Ethonal in the gas in many states that only adds to carb problems.
 
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