Yanmar 1GM User Manual page 101

SINGLE-CYLI NDER ENGINES
Straight edge
~ -=o
Feeler
--.....~ ~
gauge \..) ___
95
5
the measurement with the specification in T able I .
If gear back lash is incorrect, replace the camsha ft
and crankshaft gears.
Bore gauge
face s. Check all core plugs for leaks and replace an y that
are suspect. Sec
Core Plug Replacement
in this chapter.
Check oil lind coo lant passages for sludge, dirt and corro-
sion wh ile c leaning. If the passages are very dirty , have
the block boi led out by a machi ne shop. Blowout all pas -
sages with compres sed air. Check the threads in the head
bolt hole s to make sure they arc clean. lf'di rty. use a tap to
restore the thre ads and remove any deposits.
2. Exam ine the bloc k for cracks To confirm sus picions
about possible leakage areas. use a mixtu re of one part
kero sene and tv..o parts engine oil. Coa t the suspected area
with this solu tion. then wipe dry and immediately apply a
solution of zinc oxide disso lved in wood alcohol. If an y
discoloration appears in the trea ted area. the block is
cracked and should be repla ced.
3. Check the flatness o f the cylinder block deck or top
su rface. Place an accurate straightedge on the b lock. If
there is any gap between the block and straightedge, mea-
sure it w ith a flat feeler gau ge (I-"ig u rc 86 ). Mea sure from
end to end and from come r to comer. Have the bloc k re-
surface d if
it
is warped more than 0.07 mm (0.0028 in.).
4 . Measure the cyl inder bore wit h a bore ga uge (Fig u re
87) for out-of-rou ndness or excessive wear as desc ribed in
Piston/Cy linder Bore Check in this chapte r. If the
cy lin-
der exceeds maximum to lerances. rcbore the cylind er.
Rcbore the cy linder if the cy linde r walls are bad ly
scuffed, scored or otherwise damage.
CYLIl'IDER BLOCK
Clea ning a nd Inspection
I. C lean the block thoroughly with solvent. Remove an y
gasket or RTV sealant residue from the machined sur-
Core
1)11l~
Replacement
Check the condition of the fron t (Figur e HH ) and rear
(f igu re H9)core plugs in the block whenever the en gine is
out ofthe boat for servic e. If an y signs of leakage or corro-
sion arc found around one core plug. repl ace both of them .