Embed Size (px)
Citation preview
8/10/2019 Types of Carburetors
http://slidepdf.com/reader/full/types-of-carburetors 1/24
Types of Carburetors
Natural or side draftUpdraft
Downdraft
8/10/2019 Types of Carburetors
http://slidepdf.com/reader/full/types-of-carburetors 2/24
Natural Draft CarburetorThis carburetor isused where thereis little space on
top of the engine.The air horizontallyinto the manifold.
8/10/2019 Types of Carburetors
http://slidepdf.com/reader/full/types-of-carburetors 3/24
Updraft CarburetorsThis type is placedlow on the engineand use a gravity
fed-fuel supply. Inother words, thetank is above thecarburetor and the
fuel falls to it.
8/10/2019 Types of Carburetors
http://slidepdf.com/reader/full/types-of-carburetors 4/24
Updraft CarburetorsEven this carburetor uses gravity to receivethe fuel from the tank, the air-fuel mixturemust be forced upward into the engine.
8/10/2019 Types of Carburetors
http://slidepdf.com/reader/full/types-of-carburetors 5/24
Downdraft CarburetorsThis carburetoroperates withlower air velocities
and largerpassages. This isbecause gravityassists the air-fuel
mixture flow to thecylinder.
8/10/2019 Types of Carburetors
http://slidepdf.com/reader/full/types-of-carburetors 6/24
Down-draft CarburetorsThe downdraftcarburetor canprovide large
volumes of fuelwhen needed forhigh speed andhigh power output.
8/10/2019 Types of Carburetors
http://slidepdf.com/reader/full/types-of-carburetors 7/24
Float-Type CarburetorA Float is a smallsealed vessel madeof brass or plastic.
It maintains aconstant level offuel in the floatbowl.
8/10/2019 Types of Carburetors
http://slidepdf.com/reader/full/types-of-carburetors 8/24
Float-Type CarburetorsThe float worksmuch like one in awatering system,
opening andclosing a needlevalve as the floatlowers or raises.
8/10/2019 Types of Carburetors
http://slidepdf.com/reader/full/types-of-carburetors 9/24
The Choke
The choke is a round disc mounted ona shaft located at the intake end ofthe carburetor.
8/10/2019 Types of Carburetors
http://slidepdf.com/reader/full/types-of-carburetors 10/24
The ChokeSince cold fuel ishard to vaporize,the choke is used
during cold enginestarts to provide arich mixture to thecarburetor in order
to get the enginestarted.
8/10/2019 Types of Carburetors
http://slidepdf.com/reader/full/types-of-carburetors 11/24
The ThrottleThe throttle is around discmounted on a shaft
beyond the mainfuel nozzle in thecarburetor.
8/10/2019 Types of Carburetors
http://slidepdf.com/reader/full/types-of-carburetors 12/24
The ThrottleIt regulates theamount of air-fuelmixture entering
the cylinder.
8/10/2019 Types of Carburetors
http://slidepdf.com/reader/full/types-of-carburetors 13/24
Load AdjustmentThe amount of fuelentering the maindischarge nozzle is
sometimesregulated by a loadadjusting needle.
8/10/2019 Types of Carburetors
http://slidepdf.com/reader/full/types-of-carburetors 14/24
Load AdjustmentMany carburetorstoday have a fixed
jet or orifice which
is preset to allowthe proper amountof flow. Thesecarburetors are
non-adjustable.
8/10/2019 Types of Carburetors
http://slidepdf.com/reader/full/types-of-carburetors 15/24
The PrimerMany small engines have hand operatedplunger called a primer. When depressed itforces additional fuel through the main
nozzle prior to starting a cold engine.
8/10/2019 Types of Carburetors
http://slidepdf.com/reader/full/types-of-carburetors 16/24
Diaphragm Carburetors
This type does not have a float,rather the difference betweenatmospheric pressure and thevacuum created in the enginepulsates a flexible diaphragm.
8/10/2019 Types of Carburetors
http://slidepdf.com/reader/full/types-of-carburetors 17/24
Diaphragm CarburetorsThe pulsation ofthe diaphragmtakes place on
every intake andcompressionstroke.
8/10/2019 Types of Carburetors
http://slidepdf.com/reader/full/types-of-carburetors 18/24
Throttle ControlsA basic manualthrottle controlconsists of either
mechanical linkageor flexible cable.
8/10/2019 Types of Carburetors
http://slidepdf.com/reader/full/types-of-carburetors 19/24
Throttle ControlsThis linkagemanually opensand closes the
throttle valve toobtain the desiredengine speed.
8/10/2019 Types of Carburetors
http://slidepdf.com/reader/full/types-of-carburetors 20/24
8/10/2019 Types of Carburetors
http://slidepdf.com/reader/full/types-of-carburetors 21/24
8/10/2019 Types of Carburetors
http://slidepdf.com/reader/full/types-of-carburetors 22/24
SummaryThe updraftcarburetor is placelow on the engine
and uses a gravityfed fuel supply.The air-fuelmixture is forced
upward into theengine.
8/10/2019 Types of Carburetors
http://slidepdf.com/reader/full/types-of-carburetors 23/24
SummaryThe downdraftcarburetoroperates with
lower air velocitiesand largerpassages.It provides larger
volumes of fuelwhen needed.
8/10/2019 Types of Carburetors
http://slidepdf.com/reader/full/types-of-carburetors 24/24
Summary
Some carburetors are either floattype or diaphragm carburetors.
The float type uses a float to maintaina constant level of fuel in the fuelbowlThe diaphragm carburetor usesdifferences in atmospheric pressureand vacuum pressure to pulsate adiaphragm to pump fuel.
