Emissions Carburetor Idle Mixture Adjustment Procedures - Tecumseh TC Series Technician's Handbook

8. Install the pump gasket over the locator pins on the
pump cover, add the pump diaphragm next, and
place the assembly on the carburetor body. Check
to see that the locator pins fit the corresponding holes
in the carburetor body. Install the pump cover
retaining screw (diag. 3-13).
9. If removed on Walbro carburetors, install a new fuel
inlet fitting in the same position as the original (diag.
3-14). When installing a new fitting, insert the tip into
the carburetor body, then coat the exposed portion
of the shank with Loctite grade A (red), then press it
in squarely using support on the opposite side to
prevent damage to the carburetor body or fitting.
Press it in until the fitting bottoms out in the carburetor
body.
10. Install the choke and throttle shaft assemblies in the
reverse order of removal. Visually check for proper
operation of the choke and throttle.
NOTE: Do not re-use old choke or throttle plate shutter screws. New screws are treated with a dry Loctite adhesive
to secure them in place.
11. If applicable, attach the air vane and torque the mounting screw to 3-5 inch pounds (.34 - .57 Nm) (diag. 3-14).
12. Newer style TC series engines use an insulator / spacer between the carburetor and cylinder. That spacer MUST
be installed, as shown, for the fuel pump to operate.
EMISSIONIZED TC CARBURETOR
The Tillotson carburetor is now an emissions grade carb. It has a married idle and high speed circuitry with limited jet
adjustments on the idle.
EMISSIONS CARBURETOR IDLE MIXTURE
ADJUSTMENT PROCEDURES
The carburetor is preset at the factory at a normal setting
required for initial engine operation.
Allow the engine to reach normal operating temperature
(after 3-5 minutes).
Set the engine speed control in the idle position. With the
engine at idle speed (Note: must be less than 2400 R.P.M.
for accurate adjustment). Using a small tip screw driver
that fits through the access hole in the limiter cap, adjust
the mixture screw slowly clockwise until the engine R.P.M.
just starts to decrease. Stop and note this screw position.
Turn the idle mixture screw slowly counterclockwise. As
the engine increases R.P.M. continue to slowly turn the
screw counterclockwise until the engine R.P.M. starts to
decrease. Note this position and turn the mixture screw
back clockwise halfway between the two engine R.P.M.
drop off positions.
Verify the engine will accelerate from low speed to high
speed and that the idle speed remains at the desired
setting.
Once adjustments are complete, center the adjustment
limiter cap between the two stops and press inward to
engage the limiter. The limiter will snap into position and
engage the adjusting screw. All future adjustments should
now be made using the adjusting slot in the limiter cap.
CAUTION: Once the limiter cap is snapped into place it is
not possible to remove the limiter or to adjust the mixture
screw beyond the limits of the limiter assembly. Make sure
that initial adjustments are made per the above procedure
prior to engaging the limiter cap.
www.SmallEngineDiscount.com
Not For Resale
THROUGH HOLE
TOWARD SPARK
PLUG
VACUUM CHANNEL
TOWARDS CYLINDER
3-14
3-15
15