Husqvarna SM 50 / 2011, Workshop Manual

Page: 80 / 150

F.14
Ed. 01-09-2010
ENGINE
Reed unit
Using a sliding gauge, measure the gap (M) between stop plates. If the measured
value does not correspond to the rated value, suitably bend stop plates.
Distance M = 17 mm (0.67 in)
Piston check
If you are reusing a used piston, check the following points:
1. Check for the presence of any bruise on piston sliding surface and seizure
(light signs of seizure can be eliminated with an abrasive stone).
2. Piston ring shall not be stuck in the corresponding groove. To clean piston
groove, you can use an old piston ring or some abrasive paper (grain
400).
3. Piston ring anti-torsional retainer shall be securely installed inside piston,
and show no signs of wear.
4. Check for piston ring wear and gap.
Piston ring gap measurement
- Install ring inside cylinder, and align it with piston (approx. 10 mm (0.39
in) under cylinder upper edge).
- Using a feeler gauge, measure piston ring gap (B).
Piston ring gap: max. 0.20 mm (0.0078 in)
Should gap be above the specified value, check piston and cylinder
for wear. If piston and cylinder wear values are within tolerance,
change piston ring.
Piston and cylinder measurement, piston assembly clearance defini -
tion
- Cylinder wear is determined by measuring cylinder with a dial gauge 10
mm (0.39 in) and 50 mm (1.97 in) below sliding surface upper edge.
- Measure cylinder diameter in both X and Y axes so as to detect any out-
of-round.
- Piston is measured at skirt, across piston pin, approx. 32 mm (1.26 in)
under piston upper edge, just above slotting.
- Piston installation clearance is calculated by deducting piston max. diam-
eter from cylinder min. diameter.