Piston And Cylinder - Husqvarna 390XP Workshop Manual

Piston and cylinder

17.1 Disassembly
CAUTION! Be careful so that dirt and
unwanted materials do not get into the
crankcase.
1. Disassemble the following parts:
• Cylinder cover.
• Spark plug.
• Carburettor.
• Muffler.
2. Unscrew the anti-vibration spring (B) from the
cylinder. See fig. 1.
3. Unscrew the four bolts on the cylinder (C). See fig. 1.
4. Carefully lift up the cylinder.
5. Cover the crankcase opening immediately with a
sheet of paper or a cloth. See fig. 2.
6. Remove one of the piston's circlips, press out the
gudgeon pin, and remove the piston. See fig. 2.
7. Remove the needle bearing from the connecting
rod's smallest end.
8. Unscrew the decompression valve (D). See fig. 1.
9. Unscrew the intake manifold.
17.2 Cleaning and inspection
Clean all parts, scrape off all the remains of any gasket
material and scrape off carbon deposits from the follow-
ing surfaces:
1. The piston crown.
2. Top of the cylinder bore (inside).
3. The cylinder exhaust port.
4. The decompression valve.
5. Base of the cylinder and/or crankcase
Do a check of:
1. Make sure that the surface coting of the
cylindersurfa is not worn. Especially in the upper
end of the cylinder.
2. That the cylinder is free of score marks. See figure
3.
3. That the piston is free of score marks. Minor
scratches can be polished off with fine emery paper.
42 - English
17 Piston and cylinder
C
Fig. 1
Fig. 2
Fig. 3
D
B