TROUBLE
SHOOTING WALBRO CARBURETORS
|
Walbro carburetors by
nature are very dependable and reliable. Once a gasoline
engine is broken-in one should not need to re-tune or
adjust the carb. If one finds begins
having to re-tune and use the choke more often than usual, rest
assured...they are having a big problem that is easily solved.
75% of the time, most problems can be traced to the internal
filter screen(s). These screens are made from super-fine metal mesh and
easily become clogged. The most obvious sign of a clogged screen
is the engine running lean on the top-end which requires re-adjustment.
As the clog gets worse, both the top end 'H' needle and the low end
'L' needle will require re-adjustment. Eventually, one will have to
choke their engine often to get it to fire up. All Walbro
carburetors have internal filter screens, however there are some that
have TWO screens ! If one has a carb with two screens, both will require cleaning
and/or replacement.
The primary
screen is located on the PUMP SIDE of the carburetor. Remove the single screw
located in the middle of the pump cover and carefully lift off the
cover & rubber gasket, noting the position of the gasket . When re-assembling the carb
make sure the pump diaphragm or gasket is
situated correctly, then re install the pump cover and screw.
REMOVING THE FILTER
SCREEN The fine metal mesh filter screen can be
easily removed using an Exacto Knife or other sharp
instrument. Catch the screen on the edge and lift up. NOTE: the visible side or "cup side" is
the debris trap. Most of the crap can easily be
seen before removing the screen. One can't properly clean
the screen without removing it entirely! The "REAL" crap
is wedged or attached onto the mesh and must be blown out from the
back side. While disassembled, it is HIGHLY
RECOMMENDED to thoroughly clean the carb of all dirt and debris before re-assembly.
Once the screen has been back-flushed, carefully re-install
the screen making certain it is completely seated as originally
installed at the factory. While the carb is disassembled carefully inspect the
diaphragm(s). Diaphragms get old and wear out. Carb
overhaul kits are cheap and easy to install and available at most
small gasoline motor or lawn mower repair shops.
If one has a Walbro carburetor with a Secondary Screen,
it is located on the "float" side of the carb, requiring the removal of 4 screws at the
corners of the float diaphragm cover, and then careful removal
of the float diaphragm. There is a brass insert as shown
in the photo above and has a screen installed below the insert. DO NOT attempt to remove the insert &
screen, damage to both will occur. All that is
required is to BACK-FLUSH the screen through either one of the
2 tuning needles. To accomplish this, close off either the 'H'
or 'L' needle, and remove the remaining needle. Using an aerosol carb cleaner, available at most auto parts stores, pressurize the carb
through the open needle hole. CAUTION!!! Do not allow carb
cleaner to get into the eyes...it is very painful and damaging to the eyes! Use of safety glasses or a face shield
is highly recommended! When the secondary screen is completely back-flushed,
the carb cleaner should flow readily through
the insert. When done, carefully re-assemble the carburetor and adjust BOTH needles back to the original factory settings or typically 1.75 turns out on
each needle. NOTE: Some carburetor
repair kits include filter screens and some don't. If the carb repair kit has the screen(s) it is highly
recommended to use them. Replacement screens are also available in
quantity. Walbro Kit Number
for all WT carbs is: K20-WAT |
