Husqvarna 2009 TE 310 Workshop Manual page 184

ENGINE REASSEMBLY
Turn the crankshaft a few times in order to set the timing elements, bring the piston
to Top Dead Center (in this condition, the mark on the cylinder head is aligned with
the two marks on the idle gear of the camshafts, as shown in the figure).
Check, by means of a feeler gauge, that the valve clearance is
0,10-0,15 mm (0.004-0.006 in.) for INTAKE and
0,15-0,20 mm (0.006-0.008 in.) for EXHAUST.
Otherwise, lift the retaining clip (A) using a hook, let the rocker arm
slide to one side, extract the pad with a pair of pliers and check the
thickness.
Depending on the result, fit a new pad (as spare parts, pads are
supplied ranging from 1.60 mm-0.063 in. to 2.60 mm-0.102 in. in
steps of 0.05 mm-0.002 in.).
The new pad thickness (S) will be:
S=(G1-G)+S1
S=new pad thickness
G1=measured valve clearance
G=correct valve clearance
S1=measured pad thickness
Reassemble the clip and rocker arm.
Check the valve clearance again.
H.38 Part. N. 8000 H0368 (09-2008)