Tank Vent - Stihl BR 500 Service Manual

Adjust the idle speed with a
tachometer. Adjust the specified
engine speeds within a tolerance of
± 200 rpm.
1. Adjust engine sped with idle
speed screw (LA) to
3,300 rpm.
2. Turn low speed screw (L)
clockwise or counter-
clockwise to obtain
maximum engine speed.
If this speed is higher than
3,700 rpm, abort the procedure and
start again with step 1.
3. Use the idle speed screw
(LA) to set engine speed
again to 3,300 rpm.
4. Set the engine speed to
2,500 rpm with the low
speed screw (L).
5. Use the high speed
screw (H) to adjust the
maximum engine speed to:
5,500 rpm on the BR 500
6,100 rpm on the BR 550
7,200 rpm on the BR 600
BR 500, BR 550, BR 600
1
Do not re-stall used caps because
they may be damaged. Always
install new limiter caps.
: Place the new limiter caps on the
adjusting screws (1+2) so that
they are positioned against the
rich stop.
a
: Push the caps onto the screws
until dimension "a" is 5 mm.
– Adjust engine idle speed,
b 6.4.1
6.5

Tank Vent

Correct operation of the carburetor
is only possible if atmospheric
pressure and internal fuel tank
pressure are equal at all times. This
is ensured by the tank vent.
2
In the event of trouble with the
carburetor or the fuel supply
system, always check and clean the
tank vent.
Check function by performing
pressure and vacuum tests on fuel
tank via the fuel hoses.
– Disconnect both hoses from the
carburetor, b 6.2.2
– Seal one of the two hoses with a
suitable plug.
– Connect the other hose to the
vacuum pump 0000 850 3501
and test fuel tank under vacuum.
27