Stihl MS 661 C-M User Manual

6 MS 661, MS 661 C-M
2.5 Tightening Torquese
DG and P (Plastoform) screws are used in polymer and light metal components. These screws form a
permanent thread when they are installed for the first time. They can be removed and installed as often as
necessary without impairing the strength of the screwed assembly, providing the specified tightening torque is
observed.
For this reason it is essential to use a torque wrench.
Use the following procedure when refitting a DG or P screw in an existing thread:
Insert the screw in the hole and rotate it counterclockwise until it drops down slightly and engages in the existing
thread. Tighten the screw clockwise to the specified torque.
This procedure ensures that the screw engages properly in the existing thread and does not form a new thread
and weaken the assembly.
Micro-encapsulated screws and screws coated with threadlocking adhesive:
Before re-installing, clean both threads (screw tap into female thread by hand and then blow out with
compressed air; clean male thread with brush), coat micro-encapsulated screws with medium-strength Loctite
242 or 243, and screws previously coated with threadlocking adhesive with Loctite (see list of screws below).
Power screwdriver setting for polymer: P and DG screws max. 500 rpm.
Do not use an impact wrench for releasing or tightening screws.
Do not mix up screws with and without binding heads.
Fastener Thread size For component Torque
Nm
Remarks
Screw M 4x8 Chain tensioner cover plate / crankcase 2.0 4)
Screw P 6x40 Cover / handlebar / handle housing 6.0
M 8 Starter post / fan housing 12.0 5)
Screw M 4x12 Brake band / crankcase 3.0 4), 5)
Collar screw M 8 Collar screw / crankcase, for bar 23.0 2)
Screw M 4x12 Cover, chain brake / crankcase 3.0 4), 6)
M 10x1 Decompression valve 14.0
Screw M 4x10 Flange / crankcase 2.5 5)
Nut M 12x0.75 Housing / heater switch 2.0 V, W
Screw M 4x12 Generator / crankcase 3.0 V, W, 5)
Collar screw M 6x26 Handlebar / PA6 bushing 6.0
Screw P 6x40 Handlebar holder / handlebar / handle
housing
6.0
Screw M 5x40x25 Hand guard / fan housing / crankcase 7.0 4), 6)
Nut M 5 Shroud / stud, cylinder 3.0
Nut M 6 Spiked bumper (chain catcher) 6.0
Locknut M 5 Spiked bumper / chain sprocket cover 6.0
Screw M 5x12 Spiked bumper / chain sprocket cover / nut 6.0
Screw M 5x12 Spiked bumper / crankcase, top 8.0 4), 6)
Locknut M 5 Spiked bumper / crankcase, top / nut 8.0

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