Piston Check; Piston Ring Gap Measurement; Piston And Cylinder Measurement, Piston Assembly Clearance Determination - Husqvarna CR 65 2012 Workshop Manual

10mm
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50mm
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y
Workshop Manual Ed. 09-2011
ENGINE OVERHAUL
CR 65 2012

Piston check

Check what follows when reusing a piston:
1. Check for any dent or seizure on the piston sliding surface (you can use a
fine grain abrasive stone to remove light seizure signs).
2. Piston ring groove: The piston ring must not get stuck in the groove. To clean
the groove use an old piston ring or abrasive paper (grain 400).
3. The piston ring retainer must be firmly placed in the piston and must not be
worn out.
4. Check piston ring wear and gap.

Piston ring gap measurement

– Insert the piston ring in the cylinder and align it with the piston (ca. 10 mm
under the cylinder upper edge).
Use a feeler gauge to measure the piston ring gap (B).
Piston ring gap: max. 0.35 mm
WARNING: If the value exceeds the indicated one check the piston ring and
cylinder wear. If the piston and cylinder wear respect the tolerances, replace
the piston ring.
Piston and cylinder measurement, and piston assembly clearance deter-
mination.
– To determine the cylinder wear, the cylinder is measured by means of a feeler
gauge placed 10 mm and 50 mm under the sliding surface upper edge.
– Measure the cylinder diameter on X and Y axes to detect any ovalization.
– The piston shall be measured on its skirt transversal to the piston pin, nearly
50 mm under the piston upper edge and nearly above the slot.
– The piston assembly clearance is obtained by subtracting the piston maximum
diameter from the cylinder minimum diameter.
Piston installation clearance: 0.065 - 0.075 mm
WARNING: If the piston installation clearance exceeds 0.09 mm, it is necessary
to fit a bigger piston. If this happens with a piston marked with "E/F", it is neces-
sary to replace both cylinder and piston.
G.8