Husqvarna FR335, Workshop Manual

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6
Cylinder and piston
502 50 18-01
502 52 42-01
505 38 13-08
The cylinder and the piston are two of the components exposed to most strain in the engine. They must
withstand, for example, high speeds, large temperature swings and high pressure. Moreover, they must be
resistant to wear. Despite these tough working conditions, major piston and cylinder failure is relatively
uncommon. The reasons for this include new coatings in the cylinder bore, new types of oil and grease and
refi ned manufacturing techniques.
When servicing these components, cleanliness is of the utmost importance. It is therefore recommended
that the cylinder and the area around it be thoroughly cleaned before being dismantled from the crankcase.
Dismantling
Dismantle the following components to make the cylinder accessible:
Starter, cylinder cover, muffl er grille, muffl er with heat guard plate, decompression
valve and spark plug.
Dismantle the air fi lter, carburettor and heat guard/distance piece (see chapter ”Fuel
system”).
Then loosen the 4 bolts holding the cylinder.
Carefully remove the cylinder
straight up by rocking it back-
wards and forwards. Make sure
that no dirt enters the crankcase.
Use a rag to cover the crankcase
opening under the
piston.
Remove the circlips from the gudgeon
pin.
Using long-nose pliers remove the gud-
geon pin circlips.
Keep your thumb over the circlip to pre-
vent it from fl ying out.
Dismantle the piston.
Push the gudgeon pin from the piston
using punch 502 52 42-01.
If the pin is too tight, carefully warm the
piston.