Preparations; Vacuum Test - Stihl BR 500 Service Manual

7.8.1

Preparations

2
1
– Remove the carburetor, b 6.2.2
– Loosen the muffler mounting
screws, b 7.6
: Seal the impulse hose (1) with a
suitable plug.
: Mount the test flange
1119 850 4201 (2) to the
manifold with suitable screws.
: Slide the sealing plate
0000 855 8106 (1) between the
muffler and cylinder exhaust port.
– Tighten the muffler mounting
screws moderately.
36
The sealing plate must completely
fill the space between the screws.
– Set the piston to top dead center.
– Perform vacuum test, b 7.8.2
– Perform pressure test, b 7.8.3
1
7.8.2

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 the
vacuum pump to detect this kind of
fault.
1
– Carry out the preparations,
b 7.8.1
: Connect suction hose (1) of
vacuum pump 0000 850 3501 to
nipple (arrow) of the test flange.
1
: Close the vent screw (1) on the
pump.
: Operate the lever (2) until the
pressure gauge (3) indicates a
vacuum of 0.5 bar.
BR 500, BR 550, BR 600
3
2