Husqvarna SM 610 2006 Workshop Manual page 79

E N G IN E O V E R H A U L IN G
C ylin d er h ea d
R em ove carbon deposits from the com bustion cham ber using a rou nded
scraper.
D o n o t u se a s h arp to o l to a vo id valve se ats a n d sp ark p lu g th read
d am a g in g .
C heck the m achined surfaces of the c ylinder head using a straight edge and a
feeler gauge taking readings at th e points show n in the figure. If th e reading at
an y point is greater than the lim it prescribed then re grind the contact surface
w ith the c ylinder.
C ylinder he ad distortion lim it: 0.0019 in.
V alve seat
T his should pocketed or recessed and there sho uld be no traces of cracks or
pitting. T o check if the seat is dam aged proceed as follow s:
- C over the valve seat w ith a unifo rm la yer of red lead paste.
- F it the valve into its seat and rotate a fe w tim es so that it leaves an im pression
in the paste. D uring this operation hold the valve stem straight w ith a chuck
vice.
- T he im pression left in the paste on the valve seat should be continuous w itho ut
breaks and the w idth of the im pres sion (W ), w hich corresponds to th e thickness
of the seat should be w ithin the fo llow ing lim its:
- W = 0.062÷0.0 7 0 in. (ne w en gine: 0.039÷0.04 7 in.).
If the thickness is not w ithin these lim its then re-cut the seat.
P roceed as follow s:
Insert the guide pin of the m iller and rotate a fe w tim es to rem ove a n y dirt from the
seat.
U sing the sam e procedure as ab ove check the valve seat. If it is dam aged or burn
it w ill require fu rther m illing.
IM P O R T A N T : re m o ve a s little m aterial as p o ssib le; th is is to p re ve n t th e
va lve ste m fro m b ein g to o clo se to th e ro c ker arm an d th u s alte rin g th e
co n tact a n g le o f th e valve .
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