Stihl MS 171 User Guide - Page 31

Vacuum Test, 8.2.3 Pressure Test, pressure remains constant for

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8.2.2 Vacuum Test Oil seals tend to fail when subjected to a vacuum, i.e. the sealing lip lifts away from the crankshaft during the piston's induction stroke because there is no internal counterpressure. A test can be carried out with pump 0000 850 1300 to detect this kind of fault. 1 533RA072 TG If the vacuum reading remains constant, or rises to no more than 0.3 bar within 20 seconds, it can be assumed that the oil seals are in good condition. However, if the pressure continues to rise (reduced vacuum in the engine), the oil seals must be replaced, b 8.3 - After finishing the test, push the ring to the right to vent the pump. - Continue with pressure test, b 8.2.3 8.2.3 Pressure Test 1 2 1 : Push the ring (1) to the right. : Operate the lever (2) until the pressure gauge (arrow) indicates a pressure of 0.5 bar. If this pressure remains constant for at least 20 seconds, the engine is airtight. - If the pressure drops, the leak must be located and the faulty part replaced. 533RA075 TG : Connect suction hose (1) of pump 0000 850 1300 to nipple (arrow). To find the leak, coat the suspect area with oil and pressurize the engine. Bubbles will appear if a leak exists. 533RA072 TG 2 1 : Push ring (1) to the left. : Operate the lever (2) until the pressure gauge (arrow) indicates a vacuum of 0.5 bar. 533RA073 TG Carry out the same preparations as for the vacuum test, b 8.2.2 - Always carry out the vacuum test before the pressure test, b 8.2.2 - After finishing the test, push the ring to the left to vent the pump - disconnect the hose. - Remove the test flange. : Connect pressure hose (1) of pump 0000 850 1300 to nipple (arrow). - Install the carburetor, b 14.3 - Loosen the muffler and remove the sealing plate. - Tighten down the muffler firmly. - Reassemble all other parts in the reverse sequence. - Tightening torques, b 3.5 30 MS 171, MS 181, MS 211

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30
MS 171, MS 181, MS 211
8.2.2
Vacuum Test
Oil seals tend to fail when subjected
to a vacuum, i.e. the sealing lip lifts
away from the crankshaft during the
piston's induction stroke because
there is no internal counterpressure.
A test can be carried out with pump
0000 850 1300 to detect this kind of
fault.
:
Connect suction hose (1) of
pump 0000 850 1300 to
nipple (arrow).
:
Push ring (1) to the left.
:
Operate the lever (2) until the
pressure gauge (arrow) indicates
a vacuum of 0.5 bar.
533RA072 TG
1
1
2
533RA073 TG
If the vacuum reading remains
constant, or rises to no more than
0.3 bar within 20 seconds, it can be
assumed that the oil seals are in
good condition. However, if the
pressure continues to rise (reduced
vacuum in the engine), the oil seals
must be replaced,
b
8.3
–
After finishing the test, push the
ring to the right to vent the pump.
–
Continue with pressure test,
b
8.2.3
8.2.3
Pressure Test
Carry out the same preparations as
for the vacuum test,
b
8.2.2
–
Always carry out the vacuum test
before the pressure test,
b
8.2.2
:
Connect pressure hose (1) of
pump 0000 850 1300 to nipple
(arrow).
533RA072 TG
1
:
Push the ring (1) to the right.
:
Operate the lever (2) until the
pressure gauge (arrow) indicates
a pressure of 0.5 bar. If this
pressure remains constant for at
least 20 seconds, the engine is
airtight.
–
If the pressure drops, the leak
must be located and the faulty
part replaced.
To find the leak, coat the suspect
area with oil and pressurize the
engine. Bubbles will appear if a leak
exists.
–
After finishing the test, push the
ring to the left to vent the pump –
disconnect the hose.
–
Remove the test flange.
–
Install the carburetor,
b
14.3
–
Loosen the muffler and remove
the sealing plate.
–
Tighten down the muffler firmly.
–
Reassemble all other parts in the
reverse sequence.
–
Tightening torques,
b
3.5
1
2
533RA075 TG