Kohler CH940 User Manual download pdf (Page 15)

Adjust Carburetor

Low Idle Speed (RPM) and Governed Idle

Adjustment

1. Low Idle Speed (RPM) Setting: Place the throttle

control into the idle or slow position. Hold the

governor lever away from carburetor so the

throttle lever is against the Idle Speed (RPM)

Adjustment Screw of carburetor. See Figure 26.

Set the low idle speed to 1200 RPM* (± 75 RPM)

by turning the low idle speed adjusting screw on

carburetor in or out. Check the speed using a

tachometer.

*NOTE: The actual low idle speed depends on the

application. Refer to the equipment

manufacturer’s recommendations. The low

idle speed for basic engines is 1200 RPM. To

ensure best results when setting the low idle

fuel needle, the low idle speed should be 1200

RPM (± 75 RPM).

2. Release the governor lever and check that the

throttle lever is in the idle position. Turn the

governed idle (outer) adjustment screw on main

control bracket to obtain the equipment

manufacturer's recommended idle speed (1400-

1800 RPM). See Figure 27.

Governed Idle

Speed Screw

High Speed

Adjustment Screw

Lean

Rich

Adjust to

Midpoint

Lean

Rich

Adjust to

Midpoint

Left Side Right Side

2. Place the throttle control into the idle or slow

position. Adjust the low idle speed to 1200 RPM*.

Follow the Adjusting the Low Idle Speed (RPM)

procedure.

3. Low Idle Fuel Needle(s) Setting: Place the

throttle into the idle or slow position.

a. Turn one of the low idle fuel adjusting needles

out (counterclockwise) from the preliminary

setting until the engine speed decreases (rich).

Note the position of the needle. Now turn the

adjusting needle in (clockwise). The engine

speed may increase, then it will decrease as

the needle is turned in (lean). Note the

position of the needle. Set the adjusting needle

midway between the rich and lean settings.

See Figure 28.

b. Repeat the procedure on the other low idle

adjustment needle.

4. Recheck/adjust the Low Idle Speed (RPM), to the

specified setting.

Figure 28. Optimum Low Idle Fuel Settings.

High Speed (RPM) Adjustment

The high speed RPM (inner) adjustment screw is

preset at the factory and normally does not need

readjustment.

Figure 27. Adjusting Governed Idle Speed Screw.

Low Idle Fuel Adjustment

NOTE: Engines will have fixed low idle or limiter

caps on the two idle fuel adjusting needles.

Step 3 can only be performed within the

limits allowed by the cap. Do not attempt to

remove the limiter caps.

1. Start the engine and run at half throttle for 5 to

10 minutes to warm up. The engine must be

warm before doing steps 2, 3 and 4.

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Kohler CH940 User Manual Page 15

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