Kohler Command PRO CH26 Owner's Manual - Page 16

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Model CH750

CH750 engines use a Keihin BK two-barrel carburetor

with fixed main jets and fixed or limiter-equipped low

idle fuel adjusting needles. See Figure 20. Adjustments

are made as follows.

Figure 20. Keihin Two-Barrel Carburetor.

Low Idle Speed (RPM) Adjustment

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

control into the idle or slow position. Set the low

idle speed to 1200 RPM* (± 75 RPM) by turning

the low idle speed adjusting screw 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).

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.

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

Low Idle Fuel Adjusters

(with limiters)

Low Idle Speed (RPM)

Adjustment Screw

Fuel Solenoid

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 21.

b. Repeat the procedure on the other low idle

adjustment needle.

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

specified setting.

Lean

Adjust to

Midpoint

Rich

Left Side

Figure 21. Optimum Low Idle Fuel Settings.

Models with Governed Idle System

An optional governed idle control system is supplied

on some CH750 engines. The purpose of this system is

to maintain a desired idle speed regardless of ambient

conditions (temperature, parasitic load, etc.) that may

change. Engines with this feature contain a small

secondary spring connected between the governor

lever and the lower adjustment tab of the main

bracket. See Figure 18. Refer to the same adjustment

procedure covered in Models with Governed Idle

System for the CH18-740 models on page 15, when

adjustments are required.

Electronic Fuel Injection (EFI) System

The EFI system is a complete, electronically-controlled

fuel management system, designed to deliver a

precisely controlled fuel flow under all operating

conditions. The electronic control unit (ECU), the brain

of the system, automatically adjusts fuel delivery and

ignition timing based upon load, speed, operating

temperature, and exhaust emission levels. The low

idle speed is the only manual adjustment possible.

The ECU continuously monitors operation of the EFI

system. If it detects a problem or fault within the

system, it will illuminate the malfunction indicator

light (MIL), which is mounted in view of the operator.

This is a signal that normal, programmed operation

has been affected, and service by an authorized Kohler

Engine Dealer is required.

Lean

Adjust to

Midpoint

Rich

Right Side