Stihl 4180 Series - Piston Ring Installation and Valve Service

47Series 4180 Powerhead
: Remove the sleeve and slip it
onto the other end of the shank.
Inner pin must point towards flat
face.
VA
249RA148
: Apply the installing tool to the
piston boss, hold the piston
steady, center the tool shank
exactly and press home until the
snap ring slips into the groove.
VA
249RA149
: Fit the snap ring (1) so that its gap
(arrow) points either up or down.
– Install the crankshaft, b 7.8.3.
VA
249RA150
– Remove the piston rings from the
piston.
– Use a piece of old piston ring to
scrape the grooves clean.
– Install new piston rings.
– Fit piston rings so that their gaps
are offset 120 degrees.
VA
249RA090
– Install the piston, b 7.8.4
7.8.5 Piston Rings