Cub Cadet LT1042 - Manual (Page 24)

24
Carburetor
NOTE: Carburetor adjustments should be made only
after the engine has warmed up.
The engines on Cub Cadet Series 1000 tractors are
equipped with a fixed main jet carburetor.
Carburetors are equipped with a idle speed adjustment
screw and a low idle fuel mixture screw.
The carburetor is designed to deliver the correct fuel-to-
air mixture to the engine under all operating conditions.
The main fuel jet is calibrated at the factory and is not
adjustable. The low idle fuel mixture screw is also set at
the factory and normally does not need adjustment.
If the engine is hard to start, runs roughly, or stalls at
low idle speed, it may be necessary to adjust or service
the carburetor.
Turning the low idle mixture screw in (clockwise)
decreases the supply of fuel to the carburetor. This
gives a leaner fuel-to-air mixture. Turning the mixture
screw out (counterclockwise) increases the supply of
fuel to the carburetor. This gives a richer fuel-to-air
mixture. Setting the screw midway between the lean
and rich position will usually give the best results.
Figure 17
Troubleshooting
If engine troubles are experienced that appear to be
fuel system related, check the following areas before
adjusting the carburetor.
• Make sure the fuel tank is filled with clean, fresh
gasoline.
• Make sure the fuel tank cap vent is not blocked and
that it is operating properly.
• If the fuel tank is equipped with a shut-off valve,
make sure it is open.
• Make sure that the in-line fuel filter is clean and
unobstructed. Replace the filter if necessary.
• Make sure fuel is reaching the carburetor. Check
the fuel lines and fuel pump for restrictions or faulty
components, replace as necessary.
• Make sure the air cleaner element is clean and all
air cleaner element components are secure.
If, after checking the items listed above, the engine is
hard to start, runs roughly, or stalls at low idle speed, it
may be necessary to adjust or service the carburetor.
Adjustment
NOTE: Engines may have a fixed idle or limiter cap on
the idle fuel adjusting screw. Step 2 can only be
performed within the limits allowed by the cap.
1. Start the engine and run at half throttle for five to 10
minutes to warm up. The engine must be warm
before performing steps 2 and 3.
2. Low Idle Fuel Screw Setting: Place the throttle
into the “idle” or “slow” position. Turn the low idle
fuel mixture screw out (counterclockwise) from the
preliminary setting until engine speed decreases
(rich). Note the position of the screw. Now turn the
mixture screw in (clockwise). The engine speed
may increase, then it will decrease as the screw is
turned in (lean). Note the position of the screw. Set
the adjusting screw midway between the rich and
lean settings. See Figure 18.
Figure 18
3. Low Idle Speed Setting: Place the throttle control
into the “idle” or “slow” position. Set the low idle
speed to 2150 RPM* (± 75 RPM) on Models
LT1042 & LT1045 (1500 RPM* (± 75 RPM) on
Models LT1046 & LT1050) by turning the low idle
speed adjusting screw in or out. Check the speed
using a tachometer.
NOTE: To ensure best results when setting the low
idle fuel Screw, the low idle speed must not exceed
2150 RPM (± 75 RPM) on single cylinder engines and
1200 RPM* (± 75 RPM) on twin cylinder engines.
Low Idle
Mixture Screw
Idle Speed
Adjustment Screw
NOTE: Single-cylinder model carburetor shown. The Fuel Mixture
Screw is the uppermost screw on twin-cylinder models.
Lean
Rich
Adjust to Midpoint