Craftsman 143.991200 Specifications download pdf (Page 25)

CHAPTER 4 GOVERNORS AND LINKAGE

GOVERNOR GEAR

WEIGHTS

THROTTLE

SPRING

GENERAL INFORMATION

Tecumseh 4 cycle engines are equipped with mechanical type governors. The governor’s function is to maintain

a R.P.M. setting when engine loads are added or taken away. Mechanical type governors are driven off the

engine’s camshaft gear. The governor follower arm rests on the center of the governor spool on center force

governors, and off to one side on other governor systems. Changes in engine R.P.M. cause the governor lever

to move the solid link that is connected from the governor lever to the throttle in the carburetor. The throttle is

opened when the engine R.P.M. drops and is closed as an engine load is removed.

This chapter includes governor assembly linkage illustrations to aid in governor or speed control assembly.

OPERATION

As the speed of an engine increases, the governor

weights on the governor gear move outward by

centrifugal force. The shape of the governor weights

force the governor spool to lift. The governor rod

maintains contact with the governor spool due to the

governor spring tension. The governor rod rotates

causing the attached outer governor lever to push the

solid link and close the throttle opening. When the

engine speed decreases, the lower centrifugal force

allows the governor weights to be pulled in by the

governor spring. The governor rod rotates and the

solid link moves the throttle to a more open position

(diag. 1).

GOVERNOR

SPOOL

GOVERNOR SHAFT

TROUBLESHOOTING

Engine operation problems where the governor is suspected to be the cause may actually be the result of

other engine system failures. Hunting (engine R.P.M. surging up and down) indicates that the engine is incapable

of maintaining a constant R.P.M. with or without an engine load. Engine overspeeding must be corrected

immediately before serious engine damage occurs. Use the applicable following procedure to diagnose a

suspected governor failure.

ENGINE OVERSPEEDING

1. If the engine runs wide open (faster than normal), shut the engine off or slow it down immediately.

2. Check the condition of the external governor shaft, linkage, governor spring, and speed control assembly

for breakage or binding. Correct or replace binding or damaged parts.

3. Follow the governor adjustment procedure and reset the governor - see "Service" in this chapter.

4. Run the engine. Be ready to shut the engine off if an overspeed problem still exists. If the problem

persists, the engine will require disassembly to inspect the governor gear assembly for damage, binding,

or wear.

5. See Chapter 9 under "Disassembly Procedure" to disassemble the engine.

6. Remove the governor gear assembly. Repair or replace as necessary.

ENGINE SURGING

1. Try to stabilize the engine R.P.M. by holding in one position the solid link between the governor arm

and the carburetor throttle, using a pliers or fingers.

2. If the engine R.P.M. stabilizes, the governor or governor adjustment should be checked. See "Service"

governor adjustment procedure in this chapter. If the engine R.P.M. does not stabilize, the engine will

require additional checks see Chapter 9 under "Troubleshooting".

3. If the problem persists after the governor adjustment, check the engine R.P.M. found on microfiche

card # 30. The R.P.M. settings are critical. If the R.P.M. setting for high and low speed are within

specification and a slight surge is experienced, increasing the engine idle R.P.M. setting slightly may

eliminate this condition.

4. Check the governor shaft or linkages for binding, wear, or improper hookup. Check the governor

spring for adequate tension or damaged condition. Repair or replace as necessary.

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Craftsman 143.991200 Specifications Page 25

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