Piston Rings; Decompression Valve - Stihl MS 661 Manual

6.8

Piston Rings

– Remove the piston, b 6.7
– Remove the piston rings from the
piston.
: Use a piece of old piston ring to
scrape the grooves (arrows)
clean.
: Install the new piston rings in the
grooves so that the radii face
upward (arrows).
: Carefully fit the piston rings over
the piston so that the radii at the
ring gap meet at the fixing pins in
the piston grooves
– they might otherwise break.
– Install the piston, b 6.7
– Reassemble all other parts in the
reverse sequence.
38
6.9

Decompression Valve

– Remove the shroud, b 6.4
: Unscrew the decompression
valve (1).
: Check the sealing cone (arrow)
on the decompression valve for
damage.
– If the sealing cone does not close
completely or shows signs of
damage, install a new
decompression valve.
– Fit the decompression valve and
screw it home by hand.
– Tighten down the decompression
valve firmly.
– Reassemble all other parts in the
reverse sequence.
1
MS 661, MS 661 C-M