John-deere stx38 User Manual download pdf (Page 53)

4/23/97

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ENGINE

TESTS AND ADJUSTMENTS

SLOW IDLE SPEED ADJUSTMENT

—CARB/EPA STX38 (SN 210001— )

& STX46

Reason:

To set engine slow idle mixture and rpm.

Equipment:

• JTO5719 Photo Tachometer

Procedure:

1. Move transaxle to neutral. Engage park brake.

Late Model Carburetors—CARB/EPA

IMPORTANT: DO NOT force the SLOW idle mixture

screw tight, this will damage the needle and

seat.

2. Put reflective tape on blower housing screen.

NOTE: On CARB/EPA carburetors, no preliminary

adjustment is required for black limiter slow

idle mixture screw, this is pre-set by

manufacturer.

3. Start and run engine at MEDIUM idle for 5 minutes

to obtain operating temperature.

4. Move throttle lever to SLOW idle position.

5. Use a photo tachometer to check engine rpm at the

blower housing screen reflective timing tape.

6. Turn

Black Limiter

SLOW idle stop screw in either

direction until specified

SLOW idle speed

of 1650

± 75 rpm

is reached.

NOTE: It may be necessary to adjust slow idle stop

screw again.

7. Recheck slow idle stop screw setting.

Specifications:

SLOW idle stop screw setting. . . . . . 1650 ± 75 rpm

NOTE: For high altitude operation (above 4000 feet),

use high altitude carburetor kit, service part

number AM119687 (1994 and above) to

prevent over rich fuel mixture and black

exhaust smoke.

ATTENTION

DO NOT attempt to adjust carburetors that meet

California Air Resource Board/Environmental

Protection Agency (CARB/EPA) restrictions

unless you are a factory trained technician with

authorization to service CARB/EPA Emissions

Carburetors. These carburetors can be identified

by the black limiter on the slow idle mixture

screw.

M58370

Black Limiter

Slow Idle Mixture Screw

Slow Idle Stop Screw

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John-deere stx38 User Manual Page 53

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