Basic Setting In Service Shop - Stihl BR 500 Service Manual

Engine stops while idling
– Turn the idle speed screw (LA)
slowly clockwise until the engine
runs smoothly.
Erratic idling behavior, engine
stops even though setting of LA
screw is correct, poor
acceleration, idle speed too high
– Idle setting is too lean. Turn the
low speed screw (L) counter-
clockwise (no further than stop)
until the engine runs and
accelerates smoothly.
Erratic idling behavior
– Idle setting is too rich. Turn the
low speed screw (L) clockwise
(no further than stop) until the
engine runs and accelerates
smoothly.
Fine-tuning the carburetor for
operation at high altitude
A minor correction may be
necessary if engine does not run
satisfactorily:
– Check the standard setting.
– Warm up the engine.
– Turn the high speed screw (H)
clockwise (leaner), but no further
than stop.
If the setting is too lean, there is a
risk of engine damage due to
insufficient lubrication and
overheating.
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6.4.2 Basic Setting in
Service Shop
The limiter caps need to be
removed only if it is necessary to
replace the high speed screw (H) or
low speed screw (L), clean the
carburetor or adjust it from scratch.
After removing the limiter caps it is
necessary to carry out the basic
setting.
1 2
– Remove the shroud with rewind
starter, b 5.9
: Push the puller (1)
5910 890 4501, with the open
side facing you, between the
limiter cap (2) and carburetor
body and pry the cap off. If the
limiter cap is stuck on the screw,
turn the puller over so that its
open side faces the carburetor
body. Pry off the limiter cap.
1
After removing the limiter caps it is
necessary to carry out the basic
setting.
– Screw both adjusting screws
down against their seats.
Make the following adjustments:
– Open the high speed screw H (1)
3 1/2 turns counterclockwise.
– Open the low speed screw L (2)
2 turns counterclockwise.
– Set the idle speed to 2,500 rpm
with the low speed screw (L).
Fine tuning with tachometer
– Check the air filter and replace it
if necessary.
If the air filter is dirty, install a new
one – do not clean.
– Check the spark arresting screen
(if fitted) and clean or replace if
necessary.
– Warm up the engine.
BR 500, BR 550, BR 600
2