6 6

4 4
1 3
2
INCLUDES
H SERIES

Service
6 Manual
4
3

6566135 (10–86) Printed in U.S.A. © Melroe Company 1996

 MAINTENANCE SAFETY
Instructions are necessary before operating or servicing machine. Read and
understand the Operation & Maintenance Manual, Operator’s Handbook and
WARNING signs (decals) on machine. Follow warnings and instructions in the manuals
when making repairs, adjustments or servicing. Check for correct function after
adjustments, repairs or service. Untrained operators and failure to follow
instructions can cause injury or death. W-2003-0903

Safety Alert Symbol: This symbol with a warning statement, means: “Warning, be alert! Your safety is
involved!” Carefully read the message that follows.

CORRECT CORRECT CORRECT

B-10731a B-12365 B-7469

Never service the Bobcat Skid- Use the correct procedure to lift or Cleaning and maintenance are
Steer Loader without instructions. lower operator cab. required daily.
WRONG WRONG WRONG

B-11799 B-15231 B-15280

Have good ventilation when Disconnecting or loosening any Never work on loader with lift
welding or grinding painted hydraulic tubeline, hose, fitting, arms up unless lift arms are held
parts. component or a part failure can by an approved lift arm support
Wear dust mask when grinding cause lift arms to drop. Do not go device. Replace if damaged.
painted parts. Toxic dust and gas under lift arms when raised Never modify equipment or add
can be produced. unless supported by an attachments not approved by
Avoid exhaust fume leaks which approved lift arm support device. Bobcat Company.
can kill without warning. Exhaust Replace it if damaged.
system must be tightly sealed.
WRONG WRONG WRONG

B-6590 B-6580 B-6589

B-16102 B-16102
Stop, cool and clean engine of Keep body, jewelry and clothing Lead-acid batteries produce
flammable materials before away from moving parts, flammable and explosive gases.
checking fluids. electrical contact, hot parts and Keep arcs, sparks, flames and
Never service or adjust loader exhaust. lighted tobacco away from
with the engine running unless Wear eye protection to guard batteries.
instructed to do so in the from battery acid, compressed Batteries contain acid which
manual. springs, fluids under pressure burns eyes or skin on contact.
Avoid contact with leaking and flying debris when engines Wear protective clothing. If acid
hydraulic fluid or diesel fuel are running or tools are used. contacts body, flush well with
under pressure. It can penetrate Use eye protection approved for water. For eye contact flush well
the skin or eyes. type of welding. and get immediate medical
Never fill fuel tank with engine Keep rear door closed except for attention.
running, while smoking or when service. Close and latch door
near open flame. before operating the loader.
Maintenance procedures which are given in the Operation & Maintenance Manual can be performed by the owner/
operator without any specific technical training. Maintenance procedures which are not in the Operation & Maintenance
Manual must be performed ONLY BY QUALIFIED BOBCAT SERVICE PERSONNEL. Always use genuine Bobcat
replacement parts. The Service Safety Training Course is available from your Bobcat dealer.
MSW01-0805
 SAFETY INSTRUCTIONS
SAFETY INSTRUCTIONS

SAFETY IS YOUR RESPONSIBILITY

We care about your safety.
The Bobcat loader is designed to give maximum operator safety; but no machine design can prevent operator error or
carelessness.
BEFORE YOU WORK ON THE BOBCAT LOADER
This SERVICE MANUAL was written to give the serviceman (mechanic) instructions
for safe adjustments and/or repairs of the Bobcat loader.
Read the complete sequence in the paragraph (Example: 4–3.1 Axle and Bearing
Removal Steps 1 thru 14) so you know the complete removal procedure before the
work is actually started.
Always use jackstands and lift arm stops so you have a safe working area around the
Bobcat loader.

B–03926

WARNING IMPORTANT

For your safety, warnings This notice shows important

are on the loader and in the procedures which must be
manual. Failure to follow followed to prevent damage
these warnings can cause to the loader.
injury or death.

641, 642, 643 Loader

–1––5 Service Manual
 SAFETY INSTRUCTIONS
FORWARD PREVENTIVE
This Service Manual gives the instructions for correct servicing, adjustment and overhauling of
MAINTENANCE
the Bobcat loader Hydraulic/Hydrostatic System, Drive System, Main Frame, Electrical System
and Engine Service.
Make reference to the Operator’s Manual for operating instructions (Starting, Daily Checks,
Loader Operation, etc.). HYDRAULIC
SYSTEM
A general inspection of the following items must be made when the Bobcat loader has had
service or repair.

1. Check hydraulic/hydrostatic fluid level, engine oil level and fuel supply.
HYDROSTATIC
2. Inspect for any sign of fuel, oil or hydraulic fluid leaks. DRIVE SYSTEM

3. Lubricate the loader.

4. Check the condition of the battery(ies) and the cables.

DRIVE
5. Inspect the air cleaner system for damage or leaks. SYSTEM

6. Check the warning lights to see if they light.

7. Check tires for wear and pressure. MAIN

8. Check the Bob–Tach for wear and see if the wedges are damaged.
FRAME

9. Check the safety items for condition (Operator Guard, Seat Belt, Seat Bar, Safety Signs
(Decals), Safety Treads, etc.).

10. Make an inspection for loose or broken parts or connections.

ELECTRICAL
SYSTEM
11. Operate the loader, checking all functions.

Check the above items. If any are in need of repair or adjustment, contact the owner. ENGINE
SERVICE

TECHNICAL
CONTENTS DATA
Page
Number
ALPHABETICAL INDEX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 ALPHABETICAL
DRIVE SYSTEM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 INDEX
ELECTRICAL SYSTEM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
ENGINE SERVICE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
HYDRAULIC SYSTEM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
HYDROSTATIC SYSTEM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
MAIN FRAME . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
PREVENTIVE MAINTENANCE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
TECHNICAL DATA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

641, 642, 643 Loader

–1––3 Service Manual
 SAFETY INSTRUCTIONS
PREVENTIVE MAINTENANCE PREVENTIVE
MAINTENANCE
Paragraph Page
Number Number
AUXILIARY CONTROL LOCKBOLT . . . . . . . . . . . . . . . . . . . 1–15 1–20

BOB–TACH . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1–13 1–19

DRIVE BELTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1–6 1–12

ELECTRICAL SYSTEM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1–7 1–13

ENGINE COOLING SYSTEMS . . . . . . . . . . . . . . . . . . . . . . . . 1–5 1–10

ENGINE SERVICE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1–3 1–4

FINAL DRIVE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1–9 1–17

FUEL SYSTEM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1–4 1–8

HYDRAULIC/HYDROSTATIC SYSTEM . . . . . . . . . . . . . . . . . 1–8 1–15

INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1–1 1–1

LIFT ARM STOP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1–16 1–20

LUBRICATION OF THE BOBCAT LOADER . . . . . . . . . . . . 1–11 1–18

OPERATOR GUARD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1–12 1–19

PIVOT PINS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1–14 1–20

SERVICE SCHEDULE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1–2 1–3

TIRE MAINTENANCE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1–10 1–17

Instructions are necessary before operating or

servicing machine. Read Operation &
Maintenance Manual, and signs (decals) on
machine. Follow warnings and instructions in
the manuals when making repairs, adjustments
or servicing. Check for correct function after
adjustments. repairs or service. Failure to
follow instructions can cause injury or death.
W–2144–0189

641, 642, 643 Loader

–1––1 Service Manual
1–PREVENTIVE MAINTENANCE
1–1 INTRODUCTION Loader Serial
Number
The Preventive Maintenance Section of this Service Manual gives general
maintenance procedures for the Bobcat loader. The other sections of the Service
Manual will give the detailed description needed for disassembly and assembly
and when replacement parts are needed.

1–1.1 Serial Number Identification

It is important to make correct reference to the Serial Number of the Bobcat loader
and/or engine when making repairs or ordering parts. It is possible that the present B–02674R
loaders do not use all the same parts as the earlier loaders. It is possible that Fig. 1–1 Loader Serial Number
different procedures are used for service repair.

1–1.2 Loader Serial Number

Engine Serial
The Bobcat loader serial number plate Number
location is on the inside of the left upright,
above the grill (Fig. 1–1).

Explanation of the Serial Number: B–02249

Fig. 1–2 (641) Engine Serial Number

XXXX M XXXX
Production Sequence (Series)
Plant Location
Model, Engine Version

1–1.3 Engine Serial Number

641 Deutz: (Fig. 1–2) The engine
serial number location is on the right Engine Serial
side of the cylinder block. Use all the Number
numbers when ordering parts for this
engine.

642 Ford: (Fig. 1–3) The engine serial Engine Serial

number location is on the right side of Number
the valve cover. Use all the numbers
when ordering parts for this engine.

643 Kubota: (Fig. 1–4) The engine

serial number location is on the left
side above the speed control arm. Use
all the numbers when ordering parts
for this engine.
B–02796 B–04940
Fig. 1–3 (642) Engine Serial Number Fig. 1–4 (643) Engine Serial Number

641, 642, 643 Loader

–1–1– Service Manual
1–2 SERVICE SCHEDULE
Maintenance work must be done at regular intervals. Failure to do so will result in damage to the Bobcat loader or the
engine. The SERVICE SCHEDULE is a guide for correct maintenance of the Bobcat loader. DO NOT change this service
schedule unless the frequency of service is increased when the Bobcat loader is operated in very hot, cold, dusty or
corrosive conditions.
SERVICE SCHEDULE HOURS

1000
100
250
300
500
8–10
50
641
642
643

ITEM SERVICE REQUIRED

Engine Air Cleaner Clean dust cup. Check condition of system. Check
condition indicator.
Engine Cooling System Check coolant level. Add coolant when level is low. Remove
debris from the radiator grill area.
Tires Check air pressure & check for damage.
Wheel Nuts Tighten nuts 70 ft.–lbs. (95 Nm) torque.
Engine Oil Check & add oil as needed.
All Pivot Points Add lubricant to all fittings.
Engine Cooling Inlet Check rear door grill & blower inlets for restriction of air flow.
Clean cooling fins & blower housing when necessary.
Indicators, etc. Check for correct operation of all.
Operator Cab Check condition of cab & fastening bolts.
Seat Belt & Seat Bar Check condition of strap & buckle & replace if damaged.
Check working condition of seat bar.
Hydraulic Fluid Check & add recommended fluid as needed.
Safety Signs (Decals) Check for damage decals or decals that are gone. Replace
as needed.
Engine Oil & Filter Change the oil & the filter.
Battery Check water level & cables.
Hydraulic Tubes & Hoses Check for damage or leaks. Replace as needed.
V–Belts Check tension & make adjustments.
Crankcase Breather Clean breather cap every oil change.
Bob–Tach Check locking levers & wedges for condition & operation.
Brakes Check operation & adjust as needed.
Chaincase Fluid Check fluid level & add as needed.
Hydraulic Filter (10 Micron) Replace the filter element (S/N 14999 & Below).
Engine Cylinder Head Bolts Tighten to correct torque after first 100 hours & adjust the
valves as needed.
Engine Air Cleaner Check system for leaks. Replace element when condition
indicator shows red.
Crankcase Breather Remove the breather & clean.
Governor Check oil level in the reservoir.
Main Frame Upright Check the torque of the bolts that hold the transmission
assembly to the upright.
Spark Arrestor Muffler Remove the plug & clean the spark chamber.
Steering Lever Pivots Grease pivot points.
Engine Cylinder Compression Check compression. Repair as needed.
Engine Fuel Filter Replace the filter element.
Universal Joint Grease U–joint.
Starting Motor Remove, clean & service as needed.
Engine Fuel Filter (Inline) Replace the element.
40 Micron Filter, Bronze (if so Replace the filter in port block.
equipped)
Hydraulic/Hydrostatic Replace breather cap.
Reservoir
Engine Compression The minimum compression reading must be at least 75%
of maximum compression reading.
Chaincase Replace fluid.
Hydraulic System Replace the fluid and filter. Clean cap and vent.

Revised Aug. 84 641, 642, 643 Loader

–1–3– Service Manual
1–3 ENGINE SERVICE (General)

AVOID INJURY OR DEATH

Stop, cool and clean engine of flammable
material. Never service or adjust loader with
engine running unless instructed to do so in
manual.
W–2061–0887

B–03858
1–3.1 Opening and Adjusting The Rear Door Fig. 1–7 Releasing Rear Door

Open the rear door to service the

engine. Pull the door latch up and to the INSET
left to release the door latch (Fig. 1–7).
The door can then be fully opened to get
to the engine.

The door latch is adjusted by loosening

the set screw. Turn the nut on the end of B–05772
the latch pin (Fig. 1–8). The door must
contact the machine at the bottom (Fig.
1–9) and the top with the lever in the
position shown in figure 1–9. It will take
approximately 50 lbs. of force to push
the latch down. When the latch is
adjusted correctly, tighten the set screw.
The set screw must be aligned with the
flat surface of the bolt.

B–04101 B–04099
Fig. 1–8 Locking Nut Fig. 1–9 Closing Door
WARNING
Keep the rear door closed when
operating the machine. Failure to
do so could seriously injure a
bystander. W–2020–1285

2
B–06858

1–3.2 Engine Lubrication System

To check the oil level, stop the engine 1
and remove the dipstick from the engine
(Fig. 1–10, 1–11, 1–12, Items 1).
3
4

B–03963
B–03965
Revised Dec. 83 Fig. 1–10 Engine Servicing (641)

641, 642, 643 Loader

–1–4– Service Manual
The oil level must be kept between
the two marks on the dipstick.

1 2
Use a good quality motor oil that has
the correct API Service Classification
(See the Chart on page 1–6).

To add oil remove the fill cap (Fig.

1–10, 1–11, 1–12, Items 2)

642 Loader Only: Check the

governor oil level every 100 hours of
loader operation. Use the following
procedure to check the oil level:

1. Remove the check plug (Fig.

1–12A, Item 1).

B–06861
Fig. 1–11 Engine Servicing (642)

2. If oil flows, the level is correct.

3. If no oil flows, remove the fill

plug (Fig. 1–12A, Item 2) and
add SAE 10W–30 or 10W–40
oil until it flows from the check
plug hole.

2
4. Install and tighten the check
plug and the fill plug.

1–3.3 Replacement Of Engine Oil B–06862

And Filter

Replace the engine oil and filter every

50 hours of loader operation.

B–03601
Fig. 1–12 Engine Servicing (643)
Revised Dec. 83 641, 642, 643 Loader
–1–5– Service Manual
 RECOMMENDED SAE VISCOSITY NUMBER
(LUBRICATION OILS FOR ENGINE CRANKCASE) Back View

C°–34–29 –23 –18 –13 –7 –1 +4 +10 +15 +21 +27 +32 +38 +43 +49 +54 +60

SAE 40 or 20W–50

SAE 10W–30

SAE 15W–40

1
SAE 5W–30 2
SAE 30W
Front View

SAE 20W–20

SAE 10W

F°–30 –20 –10 0 +10 +20 +30 +40 +50 +60 +70 +80 +90 +100 +110+120+130+140

TEMPERATURE RANGE ANTICIPATED BEFORE NEXT OIL CHANGE

(GASOLINE: USE API CLASSIFICATION SE OR SF)
(DIESEL: USE API CLASSIFICATION CC OR CD)

B–06863
Fig. 1–12A Governor OIl Level Check

2
To replace engine oil and filter:

1. Operate the engine for approximately 15 minutes. Stop the engine.

2. Remove the oil plug (641, Fig. 1–10, Item 3) (642, Fig. 1–13, Item 1) (643,
Fig. 1–14, Item 1).

3. Remove the oil filter (641, Fig. 1–10, Item 4) (642, Fig. 1–13, Item 2) (643,
Fig. 1–12, Item 3).
1
4. Clean the filter housing surface. Put clean oil on the gasket of the new filter.
Install the filter and tighten the filter hand tight.

5. Install the oil plug. Remove the oil filler cap (641, Fig. 1–19, Item 2) (642, Fig.
1–11, Item 2) (643, Fig. 1–12, Item 3).
B–04260
6. Put in the correct oil (See the chart above). Put in the correct amount of oil
(641, See Paragraph 8A–1.8, Page 8A–2) (642, See Paragraph 8B–1.8, Fig. 1–13 Oil Plug (642)
Page 8B–2) (643, See Paragraph 8C–1.7, Page 8C–2).

7. Start the engine and let it run for 5

minutes. Stop the engine. Check for
leaks at the filter. Check the oil level
and add oil until the oil level is at the
top mark on the dipstick.

NOTE: DO NOT over–fill the crankcase

with oil.
1

C–02633
Fig. 1–14 Oil Plug (643)

Revised Dec. 83 641, 642, 643 Loader

–1–6– Service Manual
1–3.4 Air Cleaner Service
1
It is important to service the air cleaner
system at regular intervals for good
engine performance and long service
life.

4
Do not replace the filter element unless
the red ring shows in the condition
indicator (641 & 643, Fig. 1–15, Item 1;
and 642, Fig. 1–16, Item 1).

The air cleaner system must be clean

and must not be damaged for good
engine performance and long service 3
life. 2
D–01535
Fig. 1–15 Air Cleaner Service (641, 643)

Service the 641 and 643 air cleaners as

follows: 1

1. Loosen the clamp on the dust cup

(Fig. 1–15, Item 2). Remove the
dust cup and the element.

2. Clean the inside of the filter

housing so the element has a
smooth surface to contact at the
seal (Fig. 1–15, Item 3).

3. Install the outer element.

3
NOTE: Replace the inner element
(Fig. 1–15, Item 4) 2
approximately every third
time unless the red ring still C–01024R
shows in the condition Fig. 1–16 Air Cleaner Service (642)
indicator after replacing the
outer element.

4. Install the dust cup with the arrows on the bottom of the cup up and tighten the
clamp.

5. Push the button on the condition indicator to remove the red ring.

6. Check that the hoses and the clamps are tight.

Service the 642 air cleaner as follows:

1. Loosen the clamp on the dust cup (Fig. 1–16, Item 2). Remove the dust cup and
the element.
2. Clean the inside of the filter housing so the element has a smooth surface to
contact the seal (Fig. 1–16, Item 3).

641, 642, 643 Loader

–1–7– Service Manual
 3. Install the new filter element.

4. Install the dust cup so the arrow on the bottom of the cup is up and tighten
the clamp.

5. Push the button, at the condition indicator (Fig. 1–16, Item 1) to remove the
red ring. 1

6. Check that the hoses and the clamps are tight.

1–4 FUEL SYSTEM

2
(641 & 643)
Use number 2 diesel fuel in the engine. During very cold temperature conditions
number 1 fuel is recommended.

(642)
Use only 90–94 octane leaded fuel in the engine. B–03854
Fig. 1–17 Fuel Filling Location (641,643)
(641, 642 & 643)

Stop and cool the engine before adding fuel.

NO SMOKING! Failure to obey warnings can
cause an explosion or fire.
W–2063–0887 4

Remove the filler cap to service the fuel tank as follows (Fig. 1–17 & 1–18, Items 3
1):

1. Use a clean approved safety container to add fuel. 2

B–03994
Fig. 1–18 Fuel Filling Location (642)
2. The key switch must be off and the engine must be cool.

3. Add fuel only in an area that has a WRONG

free movement of air and no open
flames or sparks. NO SMOKING

X
(Fig. 1–19).

4. Use only clean fuel of the correct

specifications.

5. Tighten the cap on the fuel tank

(Fig. 1–17 & 1–18, Items 1).

1–4.1 Fuel Filter (641)

The fuel filter is installed on the right
upright in the engine compartment. To
replace the element:
1. Close the fuel line shut off valve B–03884
(Fig. 1–17, Item 2).
Fig. 1–19 Fuel Filling Procedure

641, 642, 643 Loader

–1–8– Service Manual
 2. Remove the filter by removing the bolt (Fig. 1–20, Item 1).
1
3. Put lubricant on the rubber gasket of the fuel filter.

4. After installing the new element, open the fuel valve and check for leaks.

1–4.1 (Cont’d) Fuel Filter (642)

There is a fuel filter in the fuel line by the fuel shut–off valve (Fig. 1–18, Item 2).
B–03959
Fig. 1–20 Fuel Filter Service (641)
Check or replace the fuel filter as follows:

1. Close the valve on the fuel line (Fig. 1–18, Item 3).
2
1
2. Loosen the nut and remove the tubeline (Fig. 1–18, Item 4).

3. Remove the filter element from the valve (turn the element clockwise).

4. Force air through the element in the direction of the arrow to check the filter.

5. Make sure the arrow is pointing in the direction of the carburetor when you
install the element.

6. Install the element. Connect the tubeline and tighten the nut. Open the valve
and check for leaks. B–03916
Fig. 1–21 Fuel Filter (643)

1–4.1 (Cont’d) Fuel Filter (643)

The fuel filter on the 643 is installed on the right upright in the engine compartment.
To replace the element:

1. Close the fuel line shut–off valve (Fig. 1–17, Item 2).

2. Remove the filter by removing the top screw (Fig. 1–21, Item 1).

3. Check the seal for damage and the surface where the seal makes contact.
Repair as needed.

4. After installing the new element open the fuel shut–off valve. Loosen the plug
on the top of the filter head (Fig. 1–21, Item 2). DO NOT tighten the plug until 1
the fuel flows from around the plug. Then tighten the plug.

5. Check for leaks.

1–4.2 Removing Air From The Fuel System (641)

After replacement of the fuel filter element or when the fuel tank has run out of fuel,
air must be removed from the fuel system before running the engine.
To remove air:

1. Loosen the slotted plug on the injector pump (Fig. 1–22, Item 1) and activate
the priming lever on the fuel pump until fuel is flowing from the loosened plug
containing no air. B–03961
Fig. 1–22 Loosen The Slotted Plug (641)

641, 642, 643 Loader

–1–9– Service Manual
 2. Loosen the pressure fitting at each injector (Fig. 1–23, Item 1) and turn the
engine until fuel flows from the fittings containing no air. Tighten the fittings.

1–4.2 Removing Air From The Fuel System (643) (Cont’d)

After replacement of the fuel filter element, or when the fuel tank has run out of B–03964
fuel, air must be removed from the fuel system before starting the engine.
Fig. 1–23 Injector Lines (641)

To remove the air:

1. Put the throttle at minimum RPM. Loosen the valve (Fig. 1–24, Item 1) on
the top of the injector pump and squeeze the bulb several times (Fig. 1–21, 1
Item 3). Turn the engine over with the starter. When the engine starts and
runs smoothly, close the valve.

1–5 ENGINE COOLING SYSTEMS

(641)
The air cooled engine must have good air circulation to cool. Keep all shrouding B–03597
installed except when cleaning the engine cooling fins. Fig. 1–24 Removing Air From Fuel System
(643)

Keep the rear door grill area free of debris and the shrouding free of leaks or dents.
If the engine overheats an inspection of the cooling system must be made. Check
for debris on the grill area and around the cylinder cooling fins. To clean the cooling
fins, remove the blower housing cover (Fig. 1–25, Item 1). Use an air hose to
remove debris from the cylinder head and blower fan (Fig. 1–25, Item 2).

1
(642, 643)
The cooling system has a coolant
recovery tank. The location of the tank 1
is on the right upright in the engine
compartment (Fig. 1–26, Item 1). 2
Remove the cap from the coolant
recovery tank to check the coolant
level. When the engine is cool, the
coolant recovery tank must be 1/3 full.
Add coolant to the coolant recovery
tank when the coolant level is low. B–03964 C–02598
Fig. 1–25 Cleaning Cooling Fins (641) Fig. 1–26 Coolant Tank (642, 643)

641, 642, 643 Loader

–1–10– Service Manual
1–5.1 Removing Coolant From The Cooling System
To remove coolant (642):
1
2

Do not remove radiator cap when the engine is

hot. You can be seriously burned.
W–2070–1285
A–02466
Fig. 1–27 Sender Switch (642)
1. Put a funnel under the temperature sender switch (Fig. 1–27, Item 1) to keep
coolant from getting into the engine compartment.

2. Remove the grill (Fig. 1–28, Item 1).

3. Remove the radiator cap (Fig. 1–28, Item 2). The grill must be removed to
do this.
4. Remove the wire (Fig. 1–27, Item
2) connected to the sender switch.
Remove the sender switch (Fig.
1–27, Item 1).

To fill the cooling system (642): 2

1. Install the sender switch (Fig.

1–27, Item 1).
2. Connect the wire (Fig. 1–27, Item
2) to the sender switch. 1
3. Premix 50% water and 50%
anti–freeze in a separate container
(See Paragraph 8B–1.8, Page
8B–2 for capacity).

4. Fill the radiator with the mixed

coolant and install the radiator cap.
B–03855
5. Install the grill (Fig. 1–28, Item 1). Fig. 1–28 Grill And Radiator Cap
6. Fill the coolant recovery tank 1/3
full.

NOTE: Protect the cooling system from freezing temperatures and

overheating by adding premixed 50/50 ethylene glycol and water to
the system.

To remove coolant from the cooling system (643):

Valve

Do not remove radiator cap when the engine is

hot. You can be seriously burned.
W–2070–1285

The valve to remove the coolant is on the left side of the engine block (Fig. 1–29). B–03599R
Fig. 1–29 Valve For Removing Coolant
Revised Dec. 83 (643)

641, 642, 643 Loader

–1–11– Service Manual
 1. Connect a hose to the valve or use
a funnel to keep coolant from
getting into the engine
compartment.
2. Remove the grill (Fig. 1–28, Item
1).

3. Remove the radiator cap (Fig. 0.500”

1–28, Item 2). The grill must be (12,7 mm)
removed to do this.
Turn the valve so that the lever is toward
the outlet of the valve.
To fill the cooling system (643):

1. Close the drain valve (Fig. 1–29).

2. Premix 50% water and 50%

anti–freeze in separate container B–03965
(See Paragraph 8C–1.7, Page Fig. 1–30 Drive Belt Adjustment (641)
8C–2 for capacity).
3. Fill the radiator and install the radiator cap.

4. Install the grill (Fig. 1–28, Item 1).

5. Fill the coolant recovery tank 1/3 full.

NOTE: Protect the cooling system from freezing temperatures and

overheating by adding premixed 50/50 ethylene glycol and water to
the system.

1–6 DRIVE BELTS

To adjust the belt tension:
(641)
1. Stop the engine.

2. Loosen the adjustment bolt and move the alternator to adjust tension at
0.500 inch (13 mm) (Fig. 1–30). Then tighten the adjustment bolt.
B–04258
(642) Fig. 1–31 Removing Belt Shield (642)

1. Stop the engine.

2. Remove the belt shield (Fig.

1–31).

3. Loosen the bolts for adjustment of

the governor (Fig. 1–32, Item 1).
Use a bar and adjust belt tension 0.500” Freeplay
to 0.500 inch (13 mm) movement (13 mm) 0.250” Freeplay
at the middle of the belt with 20 lbs. 1 (6,5 mm)
(9,07 kg) pressure (Fig. 1–32). 2
Tighten the bolts.

4. Loosen the bolts for alternator

adjustment (Fig. 1–32, Items 2 &
3). Move the alternator until the
belt has 0.250 inch of movement
at the middle of the belt with 20 lbs. 3
(9,07 kg) pressure. Tighten bolts.

5. Install the belt shield. B–02661

Fig. 1–32 Drive Belt Adjustment (642)

Revised Dec. 83 641, 642, 643 Loader

–1–12– Service Manual
NOTE: When the governor has been moved, the rod to the throttle must be
adjusted (See Paragraph 7B–2.4, Page 7B–3).
0.3125” Freeplay
(643) (8 mm)
1. Stop the engine.
2. Loosen the adjustment bolt and move the alternator to adjust tension at
0.3125 inch (8 mm). Then tighten the adjustment bolt.

1–7 ELECTRICAL SYSTEM SERVICE (See Section 6 (Electrical System) for

more information.)

1. Battery cables must be clean and tight. Remove any acid or corrosion from B–03597
the battery and cables with a baking soda and water solution (Fig. 1–34). Fig. 1–33 Adjusting Drive Belt (643)
Cover the terminals with Clark Battery Saver to prevent corrosion. Install the
covers on the terminals.

2. Two 25 ampere fuses are installed in the dash panel. If the fuses become
damaged, replace them with the same type and size fuses.

1–7.1 Using An Extra Battery

If it is necessary to use an extra battery to start the engine.

BE CAREFUL! This is a two person operation. There must be
one person in the operator’s seat and one person to connect
and disconnect the battery cables.

Keep arcs, sparks, flames and lighted tobacco

away from batteries. When jumping from
booster battery make final connection
(negative) at engine frame.
Do not jump start or charge a frozen or damaged
Batteries contain acid which burns eyes and battery. Warm battery to 60°F. (16°C.) before
skin on contact. Wear goggles, protective connecting to a charger. Unplug charger before
clothing and rubber gloves to keep acid off connecting or disconnecting cables to battery.
body. Never lean over battery while boosting, testing
or charging.
In case of acid contact, wash immediately with
water. In case of eye contact get prompt medical Battery gas can explode and cause serious
attention and wash eye with clean, cool water injury.
W–2066–1296
for at least 15 minutes.
If electrolyte is taken internally drink large
quantities of water or milk! DO NOT induce
vomiting. Get prompt medical attention.
W–2065–1296

1. The ignition must be in the off position.

2. Use an extra battery of the same voltage as the loader battery.

3. Battery terminals have identification marks. The positive terminal is marked

(+) and the negative terminal is marked (–).

4. The negative terminal (–) of the battery must be connected to the engine.

A–02741
Fig. 1–34 Cleaning Battery Posts

Revised Dec. 83 641, 642, 643 Loader

–1–13– Service Manual
 Connects to the
Starter

WARNING Connects to the

Engine for Ground Connects to the
Engine for Ground

Keep arcs, sparks, flames and

lighted tobacco away from
batteries. When jumping from
booster battery make final
connection (negative) at
engine frame.
Do not jump start or charge a
frozen or damaged battery.
Warm battery to 60°F. (16°C.) LOADER
before connecting to a BATTERY
charger. Unplug charger Booster
before connecting or Cables
disconnecting cables to EXTRA
battery. Never lean over battery BATTERY
while boosting, testing or
charging.
Battery gas can explode and
cause serious injury. B–03711R
W–2066–1296 Fig. 1–35 Connecting Booster Cables

5. Connect the end of the first cable to the positive terminal (+) of the booster battery. Connect the other end of the same
cable to the positive terminal (+) of the loader battery (Fig. 1–35).
6. Connect the end of the second cable to the negative terminal (–) of the booster battery. Connect the other end of
the second cable to the engine. DO NOT connect the cable directly to the negative terminal (–) of the loader battery.
Connecting the cable directly to the negative terminal (–) of the loader battery can cause a spark and destroy the
battery and cause personal injury.
7. Keep the cables away from the fans and belts.
NOTE: The operator must be in the operator’s seat and have the seat belt fastened.
8. Start the engine.
9. After the engine has started, remove the cable connected to the engine.
10. Then remove the cable from the loader battery post positive terminal (+).

Damage to the alternator can occur if:

• Engine is operated with battery cables
disconnected.
• Battery cables are connected when using a
fast charger or when welding on the loader.
(Remove both cables from the battery.)
• Extra battery cables (booster cables) are
connected wrong.
I–2023–1285

1–7.2 Installing A New Battery

1. Remove the battery cables (Fig. 1–36). Remember the position of the positive
terminal and the negative terminal so you can connect the cables correctly
after the new battery is installed. B–03709
Fig. 1–36 Removing Cables

Revised Dec. 83 641, 642, 643 Loader

–1–14– Service Manual
 2. Remove the battery holddown clamp (Fig. 1–37, Item 1). Remove the battery
from the engine compartment.
1
3. Clean the terminal posts (Fig. 1–38) of the new battery in the engine
compartment. Install the holddown clamp.
NOTE: DO NOT touch any metal with the battery terminals.

4. Install and tighten the battery cables. Connect the ground (negative) cable
last to prevent sparks.

1–8 HYDRAULIC/HYDROSTATIC SYSTEM (For more information see

sections 2 and 3). B–04001
Fig. 1–37 Battery Holddown Clamp
The hydraulic and hydrostatic systems use the same hydraulic oil reservoir.

The system has an engine driven vane

pump that supplies hydraulic oil to the
control valve and the lift and tilt cylinders.
Oil also goes from the control valve to the
hydrostatic transmission pumps to
provide charge pressure and cooling.

A 10 micron filter is installed on the right

side of the engine compartment (Fig.
1–39, Item 1). This filter is used to clean
the oil for the hydrostatic transmission.

The location of the oil cooler is above the

engine. The oil cooler is used for cooling
the hydraulic oil before it returns to the
vane pump.
B–03707
Fig. 1–38 Cleaning Battery Terminals

1–8.1 HYDRAULIC/HYDROSTATIC OIL RESERVOIR

Use only recommended oil in the hydraulic system (Clark Bobcat fluid [P/N
6563328]or 10W–30, 10W–40 class SE motor oil [5W–30 at temperatures below
10°F. (–23°C.)])

1
1–8.2 Checking And Adding Oil
To check the oil level in the hydraulic reservoir:

1. Put the loader on a level surface.

C–02598
Fig. 1–39 10 Micron Filter

641, 642, 643 Loader

–1–15– Service Manual
 2. Open the bottom check valve on
the side of the reservoir (Fig.
1–40, Item 1). The oil level is good
3
if the oil flows. If no oil flows, close
the valve and proceed with step 3.

3. Open the top check valve (Fig.

1–40, Item 2). Remove the fill cap
from the reservoir (Fig. 1–40, Item
3). Add oil to the reservoir until oil 2
flows at the top check valve. Close
the valve and replace the fill cap.

B–03927 B–04894
Fig. 1–40 Hydraulic Level Check Fig. 1–41 Removing Hose (641)

1–8.3 Removing Hydraulic Oil

Remove the oil from the hydraulic
reservoir and replace it with new oil
every 1000 hours of operation. Also
replace the oil after it has become dirty
and after any major repairs.

1. Remove the hydraulic filter

element. Remove the hose from
the filter housing (641, Fig. 1–41)
(642 & 643, Fig. 1–42). Let the oil
flow into a container (Fig. 1–43). B–04881 B–04880
Fig. 1–42 Removing Hose (642 & 643) Fig. 1–43 Draining Oil

2. Connect the hose to the filter housing when the reservoir is empty. Install a
new filter element.

3. Remove the snap ring and remove the screen from the fill pipe (Fig. 1–44).
Wash the screen in clean solvent and install it in the fill pipe.

4. Open the top check valve (Fig. 1–40, Item 2). Remove the fill cap from the
reservoir (Fig. 1–40, Item 3). Add oil to the reservoir until the oil flows at the
top check valve (Refer to Technical Data for type of oil to use). Close the
check valve and replace the fill cap. DO NOT fill above the top check plug
level.

C–02602
Fig. 1–44 Snap Ring

641, 642, 643 Loader

–1–16– Service Manual
1–8.4 Replacement Of The Hydraulic Filter
Replace the hydraulic filter every 100 hours of operation.

To replace the hydraulic filter element:

1. Remove the filter element (Fig. 1–45, Item 1). Let the oil flow into the 1
container.

2. Clean the surface of the filter head where the filter element makes contact
with the filter head.

3. Lubricate the rubber gasket on the filter element with oil.

4. Install the filter element. Tighten the filter by hand only.

5. Check for leaks after you operate the Bobcat loader. C–2598R
Fig. 1–45 Filter Element

1–9 FINAL DRIVE TRANSMISSION (CHAINCASE)

The chaincase contains the final drive sprocket and the chains. The chaincase is
filled with the same type of oil as the hydraulic/hydrostatic system for chain
lubrication. Refer to TECHNICAL DATA Section 8.

To check the chaincase oil level:

1. Put the Bobcat loader on a level surface.

2. Remove the plug at the front of the transmission housing (Fig. 1–46, Item
1).

3. Add oil through the check plug hole until the oil flows from the check plug
hole. Install the plug.

See Paragraph 4–5.1, Page 4–13 to drain the chaincase.

1–10 TIRE MAINTENANCE

Check the tires regularly for wear, damage and correct pressure. See
TECHNICAL DATA Section 8.

Check for loose wheel nuts. Correct torque is 65 ft.–lbs. (88 Nm) torque. 1

C–02037
Fig. 1–46 Chaincase Plug

641, 642, 643 Loader

–1–17– Service Manual
1–10.1 Tire Rotation

Hydraulic Chain Case

When two tires become worn more than Reservoir
the other two tires put the two worn tires
on the same side. The front tires must be
moved to the rear and the rear tires to
the front to keep the tire wear even (Fig.
1–47).

When new tires are installed, always

keep the tires of the same size on the
same side of the Bobcat loader.

NOTE: Both wheels, on each side of

the Bobcat loader are Coolant
connected together and are Grease
Transmission
driven at the same speed, so Oil Filter Grease
the tires must be the same C–1965R
size.
Fig. 1–47 Tire Rotation

AVOID INJURY
6561387
Do not put fluid in the tires on this machine. Fig. 1–48 Lubrication Points
W–2029–1285

1–11 LUBRICATION OF THE BOBCAT LOADER

Lubricate the Bobcat loader as specified in the Service Schedule on page 1–3 for
best performance of the Bobcat loader.
See figure 1–48 for the location of grease fittings.

Always use a good quality lithium based

multi–purpose grease when you
lubricate the Bobcat loader. Apply
lubricant until the extra grease shows.

Grease the universal joints and spline

(Fig. 1–49, Item 1) every 250 hours.

Lubricate the seat rails for easy

movement when you adjust the seat
(Fig. 1–50, Item 1).

1
B–03371R B–03925
Fig.1–49 Grease Universal Joints Fig. 1–50 Lubricating Seat

Revised Aug. 84 641, 642, 643 Loader

–1–18– Service Manual
Add oil as needed to the steering control
shaft (Fig. 1–51, Item 1). Add grease to
steering pivot bearings (Item 2) every
250 hours.

1
2

1–12 OPERATOR GUARD

2
The Bobcat loader has an operator
guard as standard equipment. The
operator guard protects the operator
from rollover and falling objects.

E–01294
Fig. 1–51 Steering Control Lubrication

Never change the operator guard by

welding, grinding, drilling holes or
adding attachments that are not
WARNING approved. This can weaken the
operator guard and cause personal
injury or death.
W–2217–1195

Check with your authorized dealer if the

operator guard has been damaged.
Make sure the operator guard fastening
bolts and nuts are tight (Fig. 1–52).

C–02599
1–13 BOB–TACH
Fig. 1–52 Tightening Operator Guard
Check the Bob–Tach for wear or Bolts
damage.
Check for free movement of wedges and
Bob–Tach levers. 1

When the Bob–Tach levers (Fig. 1–53,

Item 1) are pushed down into the locked
position, the wedges must extend far
enough to engage into the holes of the
attachment (Fig. 1–54).
Replace wedges that are bent or broken.

C–02204R B–03893
Fig. 1–53 Bob–Tach Fig. 1–54 Wedges

Revised Aug. 84 641, 642, 643 Loader

–1–19– Service Manual
1–14 PIVOT PINS

1
All pivot points, lift arms, Bob–Tach and
cylinders have large pins that are held in
position with lockbolts (Fig. 1–55, Item
1). Check that the lockbolts are
tightened to 8–10 ft.–lbs. (11–13 Nm)
torque. Do not overtighten.

B–03858
1–15 AUXILIARY CONTROL Fig. 1–55 Pivot Pin Lockbolts
LOCKBOLT

The auxiliary control has a lockbolt (Fig.

1–56, Item 1) that must be removed
before you can use the auxiliary
hydraulics (Fig. 1–57). The operator
guard must be lifted before removing the
lockbolt.
1

1–16 LIFT ARM STOP (Fig. 1–58)

1. Two persons are needed to install

the lift arm stop. One person must
be in the operator’s seat, with the
seat belt fastened, until the lift arm
C–02173R B–03856
stop is installed.
Fig. 1–56 Auxiliary Lockbolt Fig. 1–57 Auxiliary Hydraulics

2. Start the engine and raise the lift arms all the way up.

3. Have a second person install the lift arm stop over the rod end of one lift
cylinder.

NOTE: Make sure the lift arm stop is tight against the cylinder rod.

4. Lower the lift arms until the top is held between the lift arms and the lift
cylinder.

5. Stop the engine.

6558015
Fig. 1–58 Lift Arm Stop

641, 642, 643 Loader

–1–20– Service Manual
SPARK ARRESTOR MUFFLER
The spark arrestor muffler must be
cleaned every 100 hours. Wear safety
goggles.

WARNING
1

Stop engine and allow the muffler

to cool before cleaning the spark
chamber. Wear safety goggles.
Failure to obey can cause serious
injury. W–2011–1285
B–04100
Fig. 1–59 Spark Arrestor Muffler (641)

1. Stop the engine.

1

2. Open the rear door.

3. Remove the plug at the bottom of the muffler (641, Fig. 1–59, Item 1) (642,
Fig. 1–60, Item 1) (643, Fig. 1–61, Item 1).

DO NOT run the engine in an area

WARNING that has materials that can cause
combustion. Wear safety goggles. B–04259
W–2309–0398 Fig. 1–60 Spark Arrestor Muffler (642)

4. Hold a block of wood over the outlet of the muffler.

5. Start the engine and run it for about 10 seconds.

1

6. Stop the engine and install the plug.

7. Close the rear door.

B–04038
Fig. 1–61 Spark Arrestor Muffler (643)

641, 642, 643 Loader

–1–21– Service Manual
 HYDRAULIC SYSTEM
Paragraph Page
Number Number
CONTROL PEDAL LINKAGE
AND LOCKS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2–10 2–22 HYDRAULIC
SYSTEM
HYDRAULIC CONTROL VALVE . . . . . . . . . . . . . . . . . . . . . . . 2–3 2–3
HYDRAULIC/HYDROSTATIC
RESERVOIR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2–7 2–20

HYDRAULIC PUMP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2–4 2–7

HYDRAULIC SYSTEM INFORMATION . . . . . . . . . . . . . . . . . 2–2 2–2

LIFT CYLINDERS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2–5 2–12

OIL COOLER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2–8 2–21

10 MICRON FILTER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2–9 2–22

TILT CYLINDER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2–6 2–18

TROUBLESHOOTING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2–1 2–1

Instructions are necessary before operating or

servicing machine. Read Operation &
Maintenance Manual, and signs (decals) on
machine. Follow warnings and instructions in
the manuals when making repairs, adjustments
or servicing. Check for correct function after
adjustments. repairs or service. Failure to
follow instructions can cause injury or death.
W–2144–0189

641, 642, 643 Loader

–2––1– Service Manual
Thank you very much
for your reading.
Please Click Here
Then Get More
Information.