Husqvarna 50 Rancher Instruction manual

50, 50 Special, 51, and 55
Workshop Manual
531 03 00-76

This workshop manual is mainly intended for Husqvarna
50, 50 Special, 51, and 55 models, but certain chapters
can also be used for other models. The manual gives
information about how to repair the saw and how to use
special tools. In order to make sure that the saw will
function properly, always use Husqvarna original spare
parts and accessories.
The information, specifications and illustrations in this
manual are based on the information in effect at time of
printing. Any improvements or changes on these models
will be included in future manual revisions.

Page
Technical Specifications
2
Service Data
3
Service Tools
4
Safety Equipment
5
Rewind Starter
6
Ignition System
7 Centrifugal Clutch
8
Lubrication System, Oil Pump
9
Anti-Vibration System
10
Fuel System
Exhaust System
12
Cylinder & Piston
13
Crankcase & Crankshaft
2
3
3
4
12
15
22
26
30
32
47
46
51

Engine
Displacement - cc (cu. in.)
Bore - mm (in.)
Stroke - mm (in.)
Max. power of speed - rpm
Idling speed - rpm
Clutch engagement speed - rpm
No load free speed - rpm
Ignition system - Electroiux
Air gap - mm (in.)
Spark plug - Champion
NGK
Electrode gap - mm (in.)
49 (3.0)
44(1 .73)
32(1 .26)
8400
2500
3700
12500
ET
0.3 (0.012)
RCJ7Y
BPMR6A
0.5 (0.020)
51 (3.1)
45(1 .77)
32(1 .26)
8400
2500
3700
12500
ET
0.3 (0.012)
RCJ7Y
BPMR6A
0.5 (0.020)
51 (3.1)
45(1 .77)
32(1 .26)
9000
2500
3700
12500
ET
0.3 (0.012)
RCJ7Y
BPMR6A
0.5 (0.020)
53 (3.2)
46(1 .81 )
32(1 .26)
9000
2500
3700
12500
ET
0.3 (0.012)
RCJ7Y
BPMR6A
0.5 (0.020)
Fuel and Lubrication System
Carburetor - Walbro
WA82 WA82 WT170
WTl 70
Fuel tank volume - Iitre (pint)
0.6 (1 .27) 0.6 (1 .27) 0.6 (1 .27) 0.6 (1 .27)
Oil tank volume - Iitre (pint) 0.3 (0.63) 0.3 (0.63) 0.3 (0.63) 0.3 (0.63)
Oil pump capacity at 6000 rpm
cc/rein. 7.0 7.0 7.0 7.0
Oil pump type Automatic Automatic Automatic Automatic
Bar and Chain
Bar length
cm
inch
Chain pitch
Chain speed
.325 m/see
3/8 m/see.
Drive link gauge - mm (in.)
Weight - kg (Ibs)
Weight with 38 cm (15 in.)
guide bar and chain - kg (Ibs)
37-45
15-18
.325
17.417t
****
1.5 (0.058)
5.2 (1 1.5)
6.2 (13.7)
37-45
15-18
.325
17.417t
****
1.5 (0.058)
5.2 (1 1.5)
6.2 (13.7)
37-49
15-20
.325 or 3/8
17.417t
20.2/7t
1.5 (0.058)
5.2 (1 1.2)
6.2 (13.7)
37-49
15-20
.325 or 3/8
17.417t
20.2/7t
1.5 (0.058)
5.2 (1 1.2)
6.2 (1 3.7)

Service Data
& Service Tools
Service Data
Leakage Test
Crankcase/cylinder
Recommended pressure: 30 kPa (0.3 kp/cm2) (4 psi)
Maximum leakage: 20 kPa/30 sec. (0.2 kp/cm2)
(3 psi/30 see)
Service tools for test:
5025038-01
Pressure gauge
5049029-02
Intake/exhaust cover plate, 2 pieces
5025046-01
Sleeves, 2 pieces
5025403-01
Sleeves, 2 pieces
Leakage Test
Carburetor
Recommended pressure: 50 kPa (0.5 kp/cm2) (7.2 psi)
Maximum leakage: No leakage permitted
Service Tools
5025006-01
5025018-01
5025019-01
5025022-01
5025026-01
5025030-09
5025030-12
5025033-01
5025038-01
5025046-01
5025070-01
5025079-01
5025083-01
5025087-01
5025099-01
5025134-02
5025161-01
5025191-01
5025194-01
5027113-01
5027114-01
5049029-02
5049090-01
5052679-12
Assembling pliers, spark plug
Allen key, 4 mm
Allen key, 3 mm
Socket spanner, 8 mm
Puller, complete
Crankshaft installation device, Model 50 serial # 9250857 and up
Crankshaft installation device
Piston Stop
Pressure gauge
Sleeves, 2 pieces
Piston mounting set
Crankshaft seal installation tool
Hook for fuel filter
Allen screwdriver with ball
Worm wheel puller
Air gap gauge, ignition
Crankshaft removal tool
Air gap gauge, spark plug
Flywheel removal tool
Test plug
Tachometer
Intake/exhaust cover plates, 2 pieces
Puller, ball bearing
Flywheel removal tool, Model 50 serial # 9250857 and up

4
The chain brake system has a strong spring under
tension. This spring activates the chain brake band when
the chain brake is engaged. The spring is located under
a cover plate that must be removed during servicing.
Anytime the cover is removed and the spring is still under
tension it may dislodge without warning. Eye protection
must be worn during disassembly and reassembly of the
chain brake.
Chain Brake
Disassembly
Disengage chain brake. Remove clutch cover retaining
nuts and withdraw cover from the chain saw.
Clean chain brake and clutch cover assembly. Engage
the chain brake by moving the hand guard forward.
Remove hand guard retaining screw. Rethread screw
into pivot sleeve two turns. Press on screw head to drive
out pivot sleeve half on the opposite side.

Turn cover over. Using a suitable punch, drive out
remaining half of pivot sleeve. Separate hand guard from
cover.
Remove the five screws and lift off the cover plate.
CAUTION !
The spring is under tension.
Always wear safety goggles for eye protection.
Using the tip of a flat bladed screwdriver, carefully lift the
end of spring out of the cover.
Press out the pin which holds the linkage arm using a
suitable punch.

Turn the cover over and press out the brake bank
retaining pin with a punch.
Check the brake band for wear. Measure the thickness
of the band. The original thickness of the brake band is
0.80 mm (0.031 in.). The brake band must be exchanged
if the band is worn anywhere along its length to 0.65 mm
(0.026 in.) or less.
If the brake band needs to be exchanged, separate the
band from the linkage by removing the screw.
Assembly
Check all chain brake parts for wear or damage and
replace with new parts if necessary. Lubricate the linkage
and pivots with thin oil.

Assemble the brake band and knee link. Insert the roll
pin into the brake band so the open side of the pin is up
as shown in photo.
Insert the linkage and band assembly into the cover.
Secure the knee link to the cover with the retaining pin.
Slide the brake spring over the linkage spring post.
Using a flat bladed screwdriver, depress the spring, then
carefully press the spring end into the cover.
Install the cover plate.

Press the front hand guard into position. Install the pivot
sleeves and screw. Pull the hand guard back to
disengage the brake.
Mount the bar, chain and chain brake to the saw. Before
running the saw, check the brake function by moving the
hand guard forward until the brake engages. With the
brake engaged, it should not be possible to rotate the
saw chain around the guide bar. Pull the hand guard
back towards the front handle to disengage the brake.
Inertia Chain Brake Function
WARNING !
The engine must be stopped for the following test.
With the engine stopped, hold the chain saw with both
hands. With the chain saw horizontal, position the bar tip
approx. 35 cm (14 in.) above a tree stump or other firm
object such as a solid wood table.