Stihl MS 661 C-M User Manual

15MS 661, MS 661 C-M
Condition Cause Remedy
Saw chain runs while engine is
idling
Engine idle speed too high Readjust idle speed screw
LA (counterclockwise)
Models with M-Tronic, idle speed
too high
Check M-Tronic with STIHL MDG 1
and troubleshooting chart, b 8.7,
adjust or calibrate control unit,
b 8.1
(setting of idle speed screw must
not be changed)
Engine speed drops quickly under
load – low power
Air filter dirty Clean air filter or replace if
necessary
Throttle shutter not opened fully Check rod
Tank vent faulty Fit new tank vent
Fuel pickup body dirty Fit new pickup body
Fuel strainer dirty Clean fuel strainer in carburetor,
replace if necessary
Leak in fuel hose between pickup
body and carburetor
Seal connections or install new fuel
hose
Setting of high speed screw (H) too
rich
Check basic carburetor setting,
correct if necessary
Models with M-Tronic, carburetor
setting too rich
Check M-Tronic with STIHL MDG 1
and troubleshooting chart, b 8.7,
adjust or calibrate control unit,
b 8.1
Main jet bores or ports blocked Clean the carburetor
Pump diaphragm damaged or
fatigued
Fit new pump diaphragm
Ignition timing wrong, flywheel out
of adjustment
– key has sheared off or slot in
flywheel is worn
Install new flywheel or key

Stihl MS 661 C-M Specifications

General

Idle speed	- RPM
Motor type	2-stroke motor
Chain pitch	3/8 \
Blade length	800 mm
Product color	Black, Grey, Orange
Automatic oiling	Yes
Engine displacement	91.1 cm³
Power source	Gasoline
Sound power level	118 dB
Vibration emission	6.9 m/s²
Sound pressure level	105 dB

Weight and Dimensions

Weight	7400 g