Stihl BR 500 - Checking; Adjusting; Valve Clearances

30 BR 500, BR 550, BR 600
When using the ZAT 3, hold it only
by the handle (4) or position it in a
safe place. Keep fingers or other
parts of body at least 1 cm away
from the spark window (3), the high
voltage connection (2), ground
connection (5) and the ground
terminal (1).
– Crank the engine quickly with the
starter (min. 1,000 rpm).
–
– Note compression pressure.
If compression pressure is below
7.5 bar, check valve clearance and
readjust if necessary, b 7.2.
If this produces no improvement,
check the cylinder, valve seat,
piston and piston rings for scores
or other damage and replace if
necessary.
The design specification is 7.5 –
8.5 bar.
If a much higher reading is obtained
(9 – 10 bar), check operation of the
decompression system and replace
if necessary, b 7.5.1.
Check and adjust valve clearances
only when engine is cold.
– Remove the shroud with rewind
starter, b 5.9
: Disconnect wires (1) and (2) from
the ignition module.
452RA078
VA
1
2
: Take the wires out of the air guide
shroud (arrow).
: Take out the screws (arrows)
: Remove the air guide shroud (1).
452RA079
VA
1
: Take out the screw (1).
– Remove the sealing ring (arrow).
–
– Remove the valve cover (2) with
gasket.
– Use combination wrench
452RA080
VA
1
2
3
4180 890 3400 to unscrew the
spark plug.
– Rotate the crankshaft until the tip
(arrow) of the flywheel lines up
with the ignition module as
shown.
452RA081
VA
7.2 Checking / Adjusting
Valve Clearances
RA_452_00_01_02.book Seite 30 Donnerstag, 16. Februar 2012 11:52 11