Jlg 40H Service Manual User Manual download pdf (Page 43)

SECTION 2 - PROCEDURES

3120240 – JLG Lift – 2-23

Before selecting the mounting location, consider the link-

age that will be required to connect the Actuator output

arm to the butterfly or fuel valve. Read the following sec-

tion on linkages before deciding on a mounting location.

1. Mount Actuator rigidly to the engine location witch

will permit a short, straight linkage to the carburetor

or fuel valve. Avoid very hot areas.

Linkage.

1/4 -28 threaded rod and low friction rod-end bearings are

recommended for linkage materials.

Keep the linkage as short and as straight as possible.

The linkage must not rub against the engine, brackets,

hoses, etc. The linkage must be free of friction and lost

motion or "slop"

The following sketch indicates the proper linkage geome-

try for most installations.

Note that the angle between the carburetor arm and the

rod is 70 degrees with the engine at idle.This is very desir-

able! Note also that the Actuator arm travels equally on

either side of a 90 degree angle with the rod. This angular

arrangement will give the proper mechanical gain for

good stability and performance. It may be necessary to

rotate the carburetor arm relative to the butterfly to

achieve this. This can usually be done, and is usually

worth the effort! Below are some workable installations,

with good linkages. Remember, the Actuator can be

turned 180 degrees on its mounting to "reverse" the

spring-loaded direction. Also the Actuator can be

Mounted in any attitude.

The needed travel of the carburetor determines how far

out the Actuator arm the rod is to be attached. Inmost

cases, The carburetor should be moved from closed to

above 10 degrees from full open as the Actuator is moved

min. to max. THEN ALTER THE LENGTH OF THE ROD

SLIGHTLY (PERHAPS.030"), SO THAT THE ACTUATOR IS

JUST OFF ITS INTERNAL STOP, AND IS PULLING THE

BUTTER-FLY AGAINST ITS STOP. This insures that the

carburetor can fully close to idle on load dumps, minimiz-

ing over speeds.

Examine the system for springs, such as carburetor return

springs. These should be removed. Some automotive car-

buretors (as opposed to industrial carburetors) contain

internal springs for accelerator pumps, etc. These may

make good governing difficult, or even impossible. For

this and other reasons, industrial carburetors are pre-

ferred.

Move the linkage slowly through its travel, and look for

any binding or unexplained forces. Correct any before

going further.

Many “governing” problems are really caused by binding

of the butterfly and its shaft in the carburetor. This is

caused by loading due to vacuum under the butterfly and

atmospheric pressure above when the engine is running.

These forces cannot be felt when the engine is not run-

ning. Therefore, start the engine while carefully controlling

the speed by hand, and feel for binding or air load forces.

Needle bearings on the butterfly shaft are available on

many industrial carburetors to deal with this problem. Any

tendency on the butterfly stick must be corrected.

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