Stihl MS 390 Instruction Manual

43MS 290, MS 310, MS 390
English / USA
Adjustment for operation at high
altitude
A slight correction of the setting may be
necessary if engine power is not
satisfactory when operating at high
altitude:
: Check standard setting.
: Warm up the engine.
: Turn the high speed adjusting screw
(H) and low speed adjusting screw
(L) clockwise (leaner)
If you make the setting too lean, the
maximum permissible engine speed
will be exceeded – risk of engine
damage.
If the engine is low on power, check the
spark arresting screen inside the muffler.
: Take off the nuts (1).
: Remove the cover (2).
: Remove the spark arresting screen
(3).
: Clean spark arresting screen if
necessary.
: If screen is damaged or coked up,
fit a new one.
: Refit the spark arresting screen –
fit the cover.
* see “Guide to Using this Manual”
Wrong fuel mix (too much engine oil in
the gasoline), a dirty air filter and
unfavorable running conditions (mostly
at part throttle etc.) affect the condition of
the spark plug. These factors cause
deposits to form on the insulator nose
which may result in trouble in operation.
Spark Arresting Screen in
Muffler*
1
1
1
139BA020 KN
139 BA021 KN
3
2
Checking the Spark Plug
000BA002 KN

Stihl MS 390 Specifications

General

Engine Displacement	64.1 cc
Chain Pitch	3/8"
Weight	6.2 kg
Guide Bar Lengths	40 to 50 cm
Fuel Capacity	0.68 l (23.0 oz)