Yanmar 1GM User Manual page 81

SINGLE-CYLINDER ENGINES
2. Check the cylinder head for sign s of oi l or water leak-
age before cleaning. Look for corrosion or foreign mate-
rial in the oil and water pa ssages.
3. Without removing the va lves, remove all depo sits from
the com bustion cham ber. Use a fine wire brush dipped in
solvent or mak e a scrape r from hardwood. Be carefu l not
to scrat ch or gouge the com bu stion cha mbe r.
4. After all carbon is removed from the combustion
cham ber and port s, clean the enti re head in solvent. Look
for cracks or other visible signs of damage. Clean the pas-
75
Feeler
gau ge
sages
with
a stiff spiral brush, then blow the particles out
with compressed air.
NOTE
If
deposits are found in the intake or exhaus t
port, remove the valves and clean the ports.
5. Clean all carbon off the piston top.
6. Cheek the cylinder head studs for damage and replace
them if necessary. Ifa stud is loose, tighten it using the fol-
low ing procedure:
a. Install two nuts on the stud as shown in Figure
18.
b. Rotate the nuts so they contact each other, then hold
one nut and tighten the other nut aga inst the first
nut.
c . Tighten the stud in the cylinder block by turning the
top nut until reaching a torque of
60
Nom
(44
ft.-lb .).
d.
Ho ld the bottom nut, loosen the top nut, and remov e
both nuts.
7. Check the threaded rocker arm support stud for dam-
aged threads. Replace it if necessary.
8. Check for warpage of the cylinder head- to-block gas-
ket surface with a straightedge and feeler gauge (F igu re
19).
Measure diagonally, as well as end to end. If the gap
exceeds 0.07 mm (0.003 in.), have the head resurfaced by
a machine shop .
In st allation
1. Make sure the cylinder head and block gasket surfac es
are clean.
5