Generac Power Systems 53187 - Manual (Page 71)

SECTION 2.4
DISASSEMBLY AND INSPECTION
i
PART 2
ENGINE MECHANICAL
VALVE PARTS:
Cylinder Head Assembly
VALVE STEM :
Use a valve spring com pressor to com press the
SPRINGS. Then, rem ove the VALVE COTTER. RE­
TAINER,
SPRING and VALVE. Also rem ove the
VALVE GUIDE SEAL.
CHECK CYLINDER HEAD W ARP:
Use a straight edge and a thickness gauge to check
w arpage on the cylinder head low er face. Check w ith
the straight edge at six (6) points, as show n in Figure
6. If w arped excessively, correct w ith a surface grinder.
MAXIMUM CYUNDER HEAD W ARP
STANDARD VALUE - LESS THAN 0.0020 INCH
REPAIR IF MORE THAN 0.005 INCH
Inspect valve stem for dam age and excessive
w ear. Replace if dam aged or w orn excessively. Use a
m icrom eter to check valve stem diam eters at locations
1,11 and III (Figure 7). If the stem is w orn beyond lim its,
replace the valve. Also check valve head thickness
(Figure 7), replace valve if w orn excessively.
Intake Valve:
Standard Diameter 0.2740-0.2744 inch
(6.955-6.97mm)
Allowable Limit 0.24 inch (6.09mm)
Exhaust Valve
Standard Diameter 0.2736-0.2740 Inch
(6.95-6.96mm)
Allowable Limit 0.2693 inch (6.84mm)
Stem end
i/^
D
Thickness of Valve Head
Standard Thickness 0.036-0.042 inch
(0.925-1.075mm)
Allowable Limit 0.0197 inch (0.5mm)
Figure 7. Valve Stem and V alve Head Inspection
VALVE TO VALVE GUIDE CLEARANCE:
Check clearance betw een valve and valve guide
(Figure 8). If beyond lim its, replace w orn parts.
Intake valve
1
/—
Standard clearance Allowable limit
0.03 to 0.06 mm 0.2 mm
Exhaust valve
Clearance
Standard clearance Allowable limit
0.04 to 0.065 mm 0.25 mm
Figure 6. Check Points for Cylinder Head Warp
Figure 8. Valve to Valve Guide Clearance
VALVE SEAT:
Alw ays check for valve guide w ear before correct­
ing valve seat. Use 15‘, 45' and 75" cutters to correct
the valve seat (Figure 9).
PAGE 2.4-2