Husqvarna 181 Instruction manual

Workshop
manual
chain saw model
101 88 11-26
181

Contents
1■TechnicalData.3
2■ServiceData—5
3■SpecialTools 7
4■Fuelsystem 11
5■Electricsystem 17
6■Lubricatingsystem 1
7■Cylinder,Piston 23
8■Crankcase,Crankshaft _
9■Starter —33
10 wCentrifugalClutch—35
11 ■SafetyEquipment 37

1
Technical Data ■
Displacement
Bore
Stroke
Poweroutput
Ignitionsystem
Ignitionadvance
Air gap
Sparkplugtype
Electrodegap
Handleheating(181SG)
Carburetor
Fueltankvolume
Oiltankvolume
Chain lubrication
Clutchdrum/sprocket
Weights
Weight sawbody incl. chain brake (empty)
Weight sawbody (empty) incl. chain brake and
18“ bar and chain
Classificationtable
80.7 cm3 (4.9 cu in)
52.0 mm (2.05”)
38.0 mm (1.5”)
4.0 kW (5.5 hp) at 140 r/s (8.400 r/rein)
Make SEM type AM 7
25° before t.d.c. at 142 r/s (8.500 r/rein)
0.30 mm (0.01 2“)
Champion RCJ 7Y
0.5 mm (0.020”)
56 watts at 120 r/s (7.200 r/rein)
Diaphragm carburetor make Tillotson type HS 216
Basic setting:
H=1.0
L=1.0
0.85 Iitres (0.22 US gallon, 0.19 Imp gallon).
Fuel mixture 4% (1 :25)
With Husqvarna Twostroke Oil 2% (1 :50)
0.50 Iitres (0.13 US gallon, 0.11 Imp gallon)
Automatic. No supply during idling. Adjustable for 4different delivery rates.
Recommended ~ositions:
Bar 18“; Pos. 2
Bar 20” and more: Pos. 3–4
Standard 7teeth. Optional 8teeth. 3/8” pitch.
6.8 kg 15.0 lb 7.0 kg 15.4 lb
8.2 kg 18.1 lb 8.4 kg 18.5 lb
CcPc
AA
BB
cc
PLEASE NOTE!
As “A” denotes smallest cylinder diameter and “C’” the largest, piston grades
should be matched or one grade smaller. Eg it is not permissible to use agrade
Bpiston in agrade Acylinder.
3

2
Service Data ■
CrankcaseAssy
v0.04 MPa (0.4 kp/cm2, 5.7 psi)
l0,01 MPa/1 min (0.1 kp/cm2, 1.4 psi per rein)
TOOIS: 5025037-01 Vacuum gauge
5025047-01 Cover plate, inlet port
5025081-01 Cover plate, exhaust port
P0.08 MPa (0.8 kp/cm2, 11.4 psi)
l0.02 MPa/30 sec (0.2 kp/cm2, 2,8 psi per 30 see)
TOOIS: 5025038-01 Pressuregauge
5025047-01 Cover plate, inlet port
5025081-01 Cover plate, exhaust port
Fueltank
PreSSUre: 0.05 MPa (0.5 kp/cm2, 7. Ip
LNo leakage permitted
:5025038-01 Pressuregauge
Starter
Make sure that it is possible to turn the pulley at least about 1/4 turn further
when the cord is pulled out completely.
Carburetor
p0.03 MPa (0.3 kp/cm2, 4.3 psi)
LNo leakage permitted
:5025038-01 Pressuregauge
.
5

3
Special Tools ■
f
5
@
5
Assembling pliers, ~:i: ‘[ “Puller compl. with screw
spark plug protector
5
5 4
5 3
5 3
Allen key
Fitting tool compl. for
crankshaft and sealing ring
@p@
-,,,$* \
9@
N
—
o
T5
Stud fitting tool
H
5 8
5
Socket spanner
5
Holding bar compl.
R
5
Ball bearing puller compl.
5
Piston sto~
5
Revolution counter
/
.5
Vacuum gauge compl.
7

3
Special Tools ■
!5 3
5 4
Allen screwdriver with ball
R)
~..
5
Retouch paint, orange 1/8 I
aC,ampingdevice
5
A5
Glue, adhesive
5
5
SEM electric system tester
5
Air gap tool
d5
Extractor sealing ring
..
5
Puller for engineblock
Q5
%Fitting drift, sealing ring
5
Loctite AA (normal locking power)
5
bLoctite AAV (strong locking power)
&
9

2■Service Data
Chainbrake
.When used with a18“ guide bar the Swed-o-Matic should release at aload on
the bar tip of 12–17 kp (26–37 lb).
Replace the brake band as soon aswear has reduced its original thickness by
more than 25~0, i.e. at least 0,75 mm (0.03”) must be left of the original
band thickness.
Fueland oil
The twostroke engine is lubricated by oil mixed with petrol in various pro-
portions depending on the type of oil used:
Ordinary twostroke oil 1:25 (4% oil)
Husqvarna Twostroke oil 1:50 (2% oil)
See also the mixing table below:
Mt
Mixing table 2% 4%
Litres Pints Litres Petrol in Petrol in Litres Petrol in Petrol in
of oil of oil of petrol Imp gallon US gallon of petrol Imp gallon US gallon
0.2 0.35 10 2,2 2.6 51.1 1,3
0.4 0.70 20 4.4 5.2 10 2.2 2.6
1.0 1.76 50 11.0 13.2 25 5.5 6.6

4
Fuelsystem I
Removalof carburetor
Remove the air filter and the fuel hose.
Remove the throttle push rod from the plastic lever with apair of flat hose
pliers.
Remove the stop switch in order to get at the left screw that retains the carbu-
retor,
Push out the choke control from the lever on the carburetor.
Loosen the screw that connects the air filter elbow to the crankcase.
Loosen the socket head screws that retain the carburetor (use the Allen key
No. 502501 8-01) and lift the carburetor off together with the air filter el-
bow and the screws.
Clean the carburetor on the outside.
Remove the metering diaphragm cover and the metering diaphragm.
Note that the centre pin of the diaphragm enters the forked end of the lever of
the needle valve,
Connect the pressure gauge 5025038-01 to the fuel inlet of the carburetor
and pump until apressure of 0.03 MPa (0.3 kp/cm2 )is reached.
Check for any leakage at the needle valve or at the gasket on the pump side.
The easiest way of locating leakages is to pour some petrol where you suspect
the leakages to be.
Loosen the screw that retains the bearing shaft of the lever and remove lever,
shaft, spring and needle valve.
Drill asmall hole in the welch plugs (approx. @2mm) and prise away the plugs
by means of apointed tool.
NOTE! Drill with care in order not to damage the carburetor housing.
Unscrew the two adjusting needles.
Remove the cover above the pump diaphragm and remove diaphragm and
gasket.
Lift off the fuel screen carefully by means of apointed tool.
11

3■Special Tools
5
Pressuregauge compl.
\
%
5
RDistance sleeve (57 mm)
*
0
o: 5
Cover plate, inlet port
o
Q
o5
\
Cover plate, exhaust port
\
o
/
&5
’Assembling pliers,
centrifugal clutch
‘,
5
Repair kit for elec-
tric cables
5
Cable clip pliers
,--’
5
\Fitting sleeve for
sealing ring
T5
U-spanner for vibration
damper
45
Hook for fuel filter

4Fuel system ■
D.....
‘%,.,,.,
‘.
When properly adjusted the lever of the needle valve shall be on alevel with the
carburetor housing surrounding it.
If the lever is located too high, the carburetor will be very sensitive as regards
the adjustment of the adjusting needles,
Atoo low lever induces bad acceleration qualities.
Check that the lever can move freely.
Make apressure test of the carburetor. Proceed as mentioned above,
Then mount gasket, metering diaphragm and cover.
NOTE!
Care should be taken to ensure that the centre pin of the diaphragm
enters the fork in the lever!
Install the adjusting needles and screw them out to the following basic posi-
tion: H=1.0 turn open. L=1.0 turn open.
Adjustmentof carburetor
Bs
Before adjusting the carburetor, proceed asfollows:
.Clean the air filter or, if necessary, replace it with anew one.
.Check the spark plug and its electrodes.
.Check that the fuel filter is not clogged.
Examine the fuel filter as follows:
Loosen the fuel hose from the carburetor and lay the chain saw on the clutch
side. Open the tank cap, If there is enough fuel in the tank, some of it now
ought to run out of the hose.
After having made the abovementioned checks you make abasic adjustment of
the carburetor needles, i.e. H=1turn open and L=1turn open.
Start the chain saw and warm it uby applying full throttle and letting it
cut into alog.
Aconstant speed for 10–20 sec indicates not only agood high speed function
of the carburetor but also agood condition overall.
Should there be asudden lean suPPly to the engine after approx. 10–20 sec
full throttle running (big speed increase), this would indicate some fault in the
fuel system.
The trouble may be caused by:
.Leakage in the pumping section of the carburetor.
.Crack in the insulating piece.
.Loose carburetor bolts.
.Incorrectly assembled or leaking gaskets.
.Tank breather valve inoperative.
.Fuel filter clogged.
NOTE!
Too lean adjustment of the carburetor would cause aconsiderable loss
of power. Adjust the carburetor in order to obtain maximum power and
not maximum speed.
13

4■Fuel system
Carburetor check
@Ps
/Clean the fuel screen and -lines with compressed air. Check the gasket and the
pump diaphragm for damage or wear.
~~~~;[email protected]
Check that the adjusting needles are straight and that their tapered ends are
Check the gasket and the metering diaphragm for damage or wear.
Check with particular care the wear on the centre pin of the diaphragm.
A
i
!f
,, ,
Check that the needle valve is not worn, neither on its seat, nor in the groove
for the lever.
Check that the needle valve lever is not worn, neither at the connection to the
needle valve nor the metering diaphragm.
Check that the filter screen near the main jet is not dirty or damaged.
Ms
Clean all fuel lines and jets with compressed air.
Replace damaged or worn parts with new ones.
Assembly
Ps
Locate the fuel screen carefully in its seating.
Locate the pump diaphragm next to the carburetor housing and then add
gasket and cover.
Tighten the four screws of the cover diagonally and evenly.
Ms
Fit new welch plugs. Install them with asuitable drift:
for the big plug: drift 08 mm
for the small plug: drift 04 mm
NOTE!
Do not press in the plugs so that they bulge inwards!
Mount needle valve, lever, spring and shaft.
Locate the spring properly!
TIP
The carburetor spare part kit has got No. 5015467-01.
12

4
Fuel system ■
Troubleshootingguide
Irregu
idlspe
xx
Engistowhaccelex
(chorequi
xxx x
“Leanou
xx x x x x
Nfusup
Difficadjust
Too “ricsup
Nidlispe
Extrneeposi
xx
x x x
xx
x
x x xx
15

4■Fuel system
AL
Adjust the idling speed by means of the throttle adjusting screw T. Try to
reach aposition where the chain isjust beginning to rotate, that isat a
comparatively high idling speed.
Put your r;ght ham-fon the front hand/e and make afine adjustment of the L-
needle with your left hand.
Fine adjustment is made asfollows:
1.
2.
3.
4.
5.
Screw in the L-needle slowly and the speed will increase. Screw in the
needle alittle further and the speed will slow down again asthe fuel supply
becomes too “lean”. Notice the position of the needle at the highest speed.
Open the L-needle again and notice the highest position. Note that the
speed slows down at “richer” supply.
Adjust the L-needle to the highest speed position. Then open it equivalent
to 10 min on aclock-face to obtain asomewhat “richer” supply to aid
acceleration.
By means of the T-needle, adjust the idling speed to 2.300 –2.500 r/rein,
ensuring that the chain does not rotate when engine is idling.
Give full throttle acouple of times to check that the engine “responds”. If
not, open the L-needle by abt 3min. Check again.
A H
Adjust the high speed needle (H) asfollows:
Apply full throttle by keeping aconstant grasp of the throttle trigger. At
correct adjustment of the H-needle the engine should be fourstroking.
Screw in the H-needle slowly until there is no more fourstroking (position A).
Then screw the needle out equivalent to 10 min on aclock-face.
Check by means of eg revolution counter No. 5025146-02 that the high idle
speed does not exceed 12.500 r/rein.
Now the carburetor adjustment is completed and you may release your hold
of the throttle trigger.
14

5
Electric system ■
A. Ignitionsystem,
troubleshooting
In all ignition testing the plug must be firmly earthed against the cylinder in
order to prevent damage to the system.
A1.
A2.
A3.
A4,
Remove the spark plug. Connect the ignition cable and “earth” the plug
against the cylinder. Check for aspark between the electrodes when you
rotate the engine by pulling smartly on the starting handle. The stop
switch should be in position 1.
If no spark occurs, try anew plug. If still no spark, check the connection
between ignition cable and spark plug protector.
if still no ignition spark between the electrodes, disconnect the short
circuiting cable from the switch. Check for aspark. Inthis case, the stop
switch isfaulty and should be exchanged.
Should there still be no ignition, remove the starter and air conductor.
Check all cables and connections. Cables that are squeezed or otherwise
damaged should be exchanged.
Check simultaneously the gap between the magnet of the flywheel and
the core of the module, The gap should be 0.30 mm. Use air gap tool
5025134-02.
If no ignition after checks A1 – A4, the igntion coil should be
exchanged by means of aspecial tester, eg our electric system tester No.
5025124-01 (see chapter 3).
If no ignition after checks A1–A 4, the ignition coil should be exchanged
and anew check made according to A1.
The last step isto change the trigger module.
Check that the gap is exactly as stated above. Use air gap tool 5025134-02.
The ignition coil and trigger module may be checked by means of aspecial
tester, eg our electric system tester No. 5025124-01 (see c 3
B.Removalof flywheel
Remove the starter and disconnect carefully the cables from the air conductor.
Lift off the air conductor. Loosen the two screws Awith Allen key No.
5025018-01 and remove the starter pawls Bwith the washers and springs.
17

6
Lubricatingsystem ■
Removalof oil pump
Remove the following parts in order to get at the oil pump:
Clutch cover, chain and bar, centrifugal clutch (left-hand threads), clutch
drum. Note the washer between the oil pump drive gear and the main bearing
seal,
Loosen the socket head screws that retain the pump. Use Allen key No.
5025019-01.
Remove the pump from the crankcase by levering around the edgesof the
housing with screwdrivers.
Lift the suction hose and oil filter out of the oil tank. Clean the parts and
change any that may be damaged.
Check if there is dirt in the suction channel (A) by rotatin9 the PumP shaft
in both directions. When the pump works properly and isfilled with oil, the
oil goesalternately through the suction channel and the compression channel
(B).
19

5H
Electricsystem
Fit holding bar No. 5025149-01 on the flywheel and loosen the nut with a
box spanner (14 mm). Fit puller No. 5025026-01 on the holding bar and re-
move the flywheel.
Assembly is made in reverse order. The flywheel nut should be tightened by
torque 30–35 Nm. Do not forget the washer under the flywheel nut! Check
the gap between flywheel and electronic unit. Use air gap tool No.
5025134-02.
Fsp
To ensure proper connection between switch spring and ignition cable, use
assembling pliers No. 5025006-01 for fitting the switch spring on the
ignition cable.
18

6
Lubricatingsystem H
Troubleshootingguide
Tomulubrica
Insufficlubric
Plasdrivgedama
Lubricaonifellposi
Leak
xxI
xx x
-
x
xxx
x
x

6■Lubricatingsystem
For cleaning, dismantle the pump as follows:
1. Remove the adjusting screw A.
2. Loosen locking screw Bagainst which the cam curve of the pump drive runs.
Check the wear of screw B. If worn, the screw should be changed.
3. Knock the edge of the pump housing against apiece of wood to make the
pump piston slide out of the casing.
Assembly
Asssembly of the oil pump is made in reverse order to dismantling.
1. Check that the sealing ring (C) on the pressure side is fitted, clean and
undamaged.
Use sleeve No. 5025052-01 to protect the sealing ring when the pump is
fitted into the crankcase.
2. After fitting the pump into the crankcase, check that the pump piston turns
easily and that the return spring returns the pump drive towards the guide
screw.

7
Cylinder,Piston ■
Removal
Lift off the cylinder cover. Remove the throttle push rod, fuel hose and choke
control from the carburetor. Remove the spark plug protector, and the spark
plug from the cylinder.
Lothe screw that connects the air filter holder to the cr
Loosen the four screws retaining the cylinder by means of Allen key No.
5025057-01.
Loosen also the two screws for the silencer support.
Lift the cylinder with silencer and carburetor.
To facilitate removal, the piston should be at the bottom dead centre.
Put aclean rag inio the crankcase opening to protect the crankcase from the
ingressof dirt, etc.
Remove the circlips on the wristpin with apair of flat hose ~liers and ~ush out
the wristpin.
Remove the silencer and the carburetor parts from the cylinder. Clean the
external surface of the carburetor of dirt and sawdust. Scrape off carbon
deposits from the exhaust port and combustion chamber.
Control
Check the following before assembly, and take the measures required:
Broken cooling fins, damaged threads or broken stud In case of severe damages, exchange the cylinder.
at exhaust port. Restore the thread by means of HeIi-Coil inserts.
Seizure marks in the cylinder wall (especially at Polish the marks with afine emery clotch to remove
exhaust port). aluminium deposits.
If the marks are deep, exchange cylinder and piston.
Surface of the cylinder wall worn (esp. at the top). Exchange cylinder and piston.
Seizure marks on the piston. Polish the marks carefully with afine file or emery cloth.
Before fitting the piston, polish the cylinder wall as stated
above. If the marks are deep, exchange the piston and, if
necessary, the cylinder.
Piston rings stuck in the groove. Remove the piston rings carefully and clean the grooves
completely before mounting the rings.
Check the wear of the piston rings by placing them in the bottom
of the cylinder. The gap between the ends of the ring should
be 2.8 mm max.
Check that the rings are still springy.
23

7
Cylinder,Piston H
Connect the choke control, fuel hose and throttle push rod to the carburetor.
Fit the screw for the air filter elbow,