Vacuum Test - Stihl MS 650 Manual

1
: Check that the pin (1) in the test
flange 1128 850 4200 is in hole
No. 1 (arrow), fit if necessary.
3
: Push the test flange (1) into
position.
: When fitting the test flange, make
sure the pin locates properly in
the impulse hose (2).
: Fit the nuts (3) and tighten them
down firmly.
MS 650, MS 660
6.3.2

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 counter-
pressure.
A test can be carried out with the
vacuum pump to detect this kind of
fault.
1
2
– Preparations – b 6.3.1
: Connect suction hose (arrow) of
vacuum pump 0000 850 3501 to
nipple (arrow) of the test flange.
3
1
: Close the vent screw (1) on the
pump.
: Operate lever (2) until pressure
gauge (3) indicates a vacuum of
0.5 bar.
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 crankcase), the oil
seals must be replaced.
– After finishing the test, open the
vent screw and disconnect the
hose.
– Continue with pressure test –
b 6.3.3
2
31