Yanmar 1GM User Manual page 134

128
5. Posit ion the engine so the valve lifters will not fall out
when the cam shaft is withdrawn.
6. Remove the bea ring retaining screw (Figu re 74 ), the n
withdraw the cam shaft.
7. Remove the valve lifters and mark them so they may
be reinstalled
in th eir original locations.
NOTE
If
precision measuring equipment is not
availab le, hOI'1! Step
8
perfo rmed by a deal-
ership or machine shop.
8. Check the bearing joumal(s) and lobes for signs of
wear or sconng.
9. Measure the bearing joumal(s) and lobes (Figure 75)
and compare the results
10
the speci fications in Ta bles
1-3. Replace the camshaft if the jou rnal or lobes do not
meet spec ifications .
10. Measure the stem diameter of the valve lifters and
co mpare
it
to the specification in Tables 1-3 . Measu re the
lifter bores in the cylinder block. Calculate the lifter clear-
ance and compare it with the spe cification in Tabl es 1-3.
Replace the valve lifters if they do not meet spcciflca-
tions. Replace the valve lifter if the lifter face is scored,
galled, excess ively worn or otherwise damaged.
II . Replace the ball bearing if it is damaged or feels
rough during rotation.
12. Installation is the reverse of removal.
Note the fol-
lowing:
a. If installing a new camshaft. coat the camshaft lobes
with camshaft break-in lubricant. If reinstalling the
original camshaft, apply heavy oil to the camshaft
lobes.
b. Lubricate the camshaft bearing jouma l(s) with
heavy engine oil before reinstallation.
c. Lightly tap the end of the camshaft to seat the ball
bearing in the engine . Rotate the camshaft to be sure
it rotates freely.
d. Align the timing marks (Fi2ure 76) on the camshaft
and crankshaft gears when installing the camshaft
gear.
c. Install the fuel injection cam so the side marked
with a zero is out (Fi2ure 77, typical).
f. Check gear backlash by installing a dial indicator as
she.... -n in Figure 67 or by rotating the gear teeth
with soft solder between the gear teeth. Compare
the measurement with the speci fication in Tables
1-3. If gear backlash is incorrect. replace the cam-
shaft and crankshaft gears.
CHAPT ER SIX
CYLINDER BLOCK
Cleaning and Inspection
I. Clean the block thoroughly with solvent. Remove any
gasket or RTV sealant residue from the machined sur-
faces. Check all core plugs for leaks and replace any that
arc suspect. See Core Plug
Replacement
in this chapter.
Check oil and coo lant passages for sludge, dirt and corro-
sion while cleaning. If the passages are very dirty, have
the block boiled out by a machine shop. Blowout all pas-
sages with compressed air. Check the threads in the head
bolt holes
to be
sure they are clean. If dirt y, use a tap to reo
store the threads and remove any deposits.
2. Examine the block for cracks. To confirm suspicions
about possible leakage areas, usc a mixture of one part
kerosene and two parts engine oil. Coat the suspected area
with this solution. then wipe dry and immediately apply a
solution of zinc oxide dissolved in wood alcohol. If any
discoloration appears in the treated area, the block is
cracked and should be replaced,
NOTE
On 2GAf. 3GM and 3JfM engines, remm 'e
the cylinder liners to check the cylinder
block deck / or warpage in Step 3.
3. Check the flatness of the cylinder block
deck
or top
surface. Place an accurate straightedge on the block. If
there is any gap between the block and straightedge, rnea-
sure it with a flat feeler gauge (F fgu re 78). Measure from
end to end and from comer to comer. Have the block re-
surfaced ifit
is warped more than 0.07 mm (0.0028 in.).
4. On 2GM20. 3GM30 and 3HM35 models- Measure
the cylinder bores with a bore gauge (f igure 79) for
out-of-roundn ess or excessive wear as described in Pis-
ton/Clylinder Bore Check in this chapter. If the cylinders
exceed maximum tolerances. they must
be
rebored.