Husqvarna K770 SmartGuard, Workshop Manual

Page: 45 / 76

examined carefully. It is important to identify the cause
of the unusual wear.
6.8.5 To examine cylinder wear
Examine the cylinder bore against the light. You can
continue to use the cylinder if the surface layer has not
been broken through. Aluminium from the piston can be
removed using emery cloth.
6.8.6 To examine the piston
The bottom of the piston, near the inlet and exhaust
ports, usually shows the largest signs of wear. Examine
the lines made by the manufacturing process. Replace
the piston if the bottom has been worn smooth. A
product with a worn piston is difficult to start because of
the decreased valve function of the piston.
6.8.7 Piston wear tolerances
6.8.7.1 Piston ring play
If the piston ring play is more than 0.006 in./0.15 mm,
the piston ring groove must be measured as set out
below.
6.8.7.2 Piston ring groove
If the piston ring groove is larger than 0.06 in./1.6 mm,
the piston must be replaced. Install a complete piston kit
with piston rings, needle bearing and wrist pin.
6.8.7.3 Piston ring wear
Put the piston ring in the cylinder with the aid of the
piston. Put it around 1 in/2.5 cm from the bottom of the
cylinder. The piston ring distance must be max. .04
in/1.0 mm.
1453 - 001 - 02.04.2020 Repair and servicing - 45