You can read this article at Jacks Small Engines as well.
Tecumseh Carburetors are fairly simple units. The float model carbs are easy to rebuild/repair. Before you
start, one thing you will need is a factory repair manual
There are some common problems with carburetors that should be checked
before you start a rebuild. Many times the following items will correct
the trouble your engine is having. You will still need a repair kit to
replace certain gaskets
and seals that should be replaced whenever disturbed.
One of the more common problems is the flooding of the carb. If this is
your complaint check the float first. Remove the float bowl, float pin
and remove the float. Be careful that you do not loosen the float
needle valve. Now shake the float and listen for gas inside. If the
float sloshes, replace it with a new one. Replace the float needle
valve seat and adjust the float per the factory manual. Replace the
float bowl gaskets.
If you are experiencing performance problems and suspect the carb, you
will have to remove it from the engine to correct the problem. After
the carb is off the engine there is one thing you need to check before
going any further. Remove the float as above. Now hold the choke and
throttle butterflies so that you can shake the carb without them making
a sound. Shake the carb and listen for it to rattle. If you do not hear
the rattle, the emulsion tube is stuck. This tube is sealed into the
body of the carb during manufacturing and can not be replaced. The
carburetor will need to be replaced. Also if the aluminum body of the
carb is corroded inside, any rebuild will only be a temporary fix. Once
the corrosion has started it can not be stopped.
If everything checks out up to here, a rebuild and cleaning should fix
the carb. However there is one more tricky thing you will need to do.
You must remove the welch plug on the side of the carb. This can be
done by driving a sharpened small punch or screw driver through the
plug and popping it out. Take extreme care when doing this procedure.
There are two jets cast into the carb body under this welch plug. If
you damage them the carb will have to be replaced. With the welch plug
removed and the main jet(in the bowl nut) out the three holes that need
to be cleaned are exposed. Using a piece of soft tag wire clean these
holes. Now clean the complete carb with carb cleaner.
Re-assemble the carb. Make sure that the needle valve seat is
completely down into its bore. After driving in the new welch plug,
paint it with finger nail polish to seal it. Adjust the float height
using a #4 twist drill as directed in the repair manual.
Now that your carb is rebuilt don't drop the ball on the 90 yard line.
Replace the gaskets between the carb and the engine, and the carb and
the air cleaner. One common mistake made is to fail to replace the fuel
line between the carb and the fuel filter/tank. If the carb was full of
dirt or varnish the fuel line will also be. Plus when the carb or fuel
line is removed, the inside of the hose usually is damaged. Small
fragments of hose materials can break loose and flow into the carb.
This will ruin the job that you just completed.
After the carb is remounted to the engine it must be adjusted
correctly. You will need a repair manual to do this. Remember that the
idle circuit must be adjusted first. Without the idle circuit working
correctly you will never get the main jet adjusted correctly