Generac Power Systems 53187 - Manual (Page 73)

SECTION 2.4
DISASSEMBLY AND INSPECTION
PART 2
ENGINE MECHANICAL
Cylinder Head Assembly (Continued)
HEAD REASSEMBLY;
Reassem ble all parts In the reverse order of disas­
sem bly. W hen assem bling the VALVE SPRING, RE­
TAINER and COTTER, use care to avoid dam age to
the VALVE GUIDE SEAL.
Cylinder Block
TOP FACE;
Inspect the cylinder block top face for dam age,
cracks, w arpage. Use the sam e m ethod that w as used
for checking the cylinder head w arp (Figure 6, Page
2.4-2). Allow able w arp lim it is the sam e as for the
cylinder head.
CYLINDER BORE;
Visually inspect the cylinder bore. There should be
no scoring, rust or corrosion. Measure thye cylinder
bore at its upper, m iddle and low er areas, at positions
A and B (Figure 14). If the bore diam eter exceeds lim its,
rebore to the correct oversize dim ension.
Front
Slide range
of piston ring
Figure 14. Checking Cylinder Bore
NO TE; In Figure 14, see "Slide Range of Piston
Ring". T he upper area corresponds to the top ring
w hen the piston Is at top dead center (TDC), or
about 0.39 Inch below the cylinder block top sur­
face. The low er area corresponds to position of oil
ring w hen the piston Is at bottom dead center (B DC)
or about 3.94 Inches from cylinder block top sur­
face.
Use a cylinder (inside diam eter) gauge to m easure
the cylinder bore.
HONING THE CYLINDERS;
After boring is com pleted, hone the cylinder in tw o
stages to obtain a diam ond or "cross-hatch" finish. See
Rgure 15. The follow ing specifications apply to honing:
□ Use a rough finishing stone that corresponds to (a)
Tokyo DIA, (b) SD120/140, (c) N100M (bronze se­
ries).
□ Use finishing stone GC600JB.
□ Use a grinding stone 100m m long by 4m m w ide (3.94
X 0.157 inch).
□ Drill speed should be 162 rpm .
□ Feed should be 13m per m inute (42.6 ft. per m inute).
□ Rough finishit^ gauge pressure should be 213 psi
(15 kg percm ^.
□ Rnjshing pressure should be 71.12 psi (5 kg per
cm ^).
□ Perform the finishing strokes nine (9) tim es.
□ Honing depths should be 0. 0015 inch (0.04m m ).
□ Cross hatch angles should be 40*.
□ Surface roughness should be 2 to 4p.
Standard bore Allowable limit
75 - 75.019 b 75.2
First boring
0.5 mm
Standard bore Allowable limit
b 75.5 ~ 75.519 b 75.7
Second
boring
0.5 mm
Standard bore Allowable limit
b 76 - 76.019 b 76.2
Replace the block
Figure IS. Cylinder Boring Specifications
Piston and Piston Rings
Use a ring com pressor to rem ove piston rings.
Rem ove one snap ring, then rem ove the piston pin
(Figure 16). W ith connecting rod and piston pin re­
m oved proceed w ith inspections as follow s.
PAGE 2.4-4