English –
41
Repair instructions
• Measure piston ring wear. This should not
exceed 1 mm. Use the piston to push down the
piston ring.
• The needle roller bearing is undamaged.
• The inlet manifold is undamaged.
• Pressure test the decompression valve.
• Also refer to Jonsered’s Analysis guide for piston
failures, art. no. 108 07 01-01.
Decompression valve – pressure
testing
1
Connect tool 502 50 38-01 to the decompression
valve.
Piston and cylinder – refitting
1
Fit the piston with the arrow pointing towards the
exhaust port. Push in the gudgeon pin and fit the
circlips. If replacing the cylinder, fit the decompres-
sion valve, tightening to a torque of 12–14 Nm.
Lubricate the little end bearing with two-stroke oil
and insert it in the connecting rod.
2
Cleaning and inspection
Clean all the components, scraping off all traces of
old gasket and carbon from the following places:
• Piston crown
• Top of the cylinder bore
• Cylinder exhaust port
• Decompression valve channel
• Cylinder base and/or crankcase
Check the following:
• The surface coating of the cylinder is not worn
through, especially in the upper part of the
cylinder.
• The cylinder is free from score marks and areas
of wear.
• The piston is free from score marks. Small
scratches can be polished out with fine emery
paper.
• The piston ring is not burnt into its groove.
2
Pump up the pressure to 80 kPa (0.8 bar).
3
Wait 30 seconds.
4
The pressure should not be less than 60 kPa
(0.6 bar).