Valve Guides; Valve Tappets; Valve Springs; Installation - Generac Power Systems GN190H Service And Repair Manual

SECTION 9: VALVE TRAIN
VALVE SERVICE (CONTINUED)

VALVE GUIDES:

Valve guides are permanently installed in the cylinder head
and cannot be replaced (see Figure 9.9).
At the time of this writing, oversize valves were NOT avail-
able. Thus, if valve guides are worn or damaged, the guides
cannot be reamed to accommodate an oversize valve stem.
DESIGN DIAMETER OF VALVE GUIDES
GN-190 = 0.218-0.217 inch (5.445-5.460mm)
GN-191 = 0.273-0.274 inch (6.965-6.980mm)
GN-220 = 0.273-0.274 inch (6.965-6.980mm)
INTAKE VALVE STEM DIAMETER
GN-190 =0.215-0.216 inch (5.465-5.480mm)
GN-191 =0.274-0.275 inch (6.965-6.980mm)
GN-220 =0.274-0.275 inch (6.965-6.980mm)
EXHAUST VALVE STEM DIAMETER
GN-190 =0.214-0.215 inch (5.445-5.460mm)
GN-191 =0.273-0.274 inch (6.965-6.980mm)
GN-220 =0.273-0.274 inch (6.965-6.980mm)
VALVE GUIDES
Figure 9.9 —
Valve Guides in Cylinder Head

VALVE TAPPETS:

Figure 9.10 — Tappet
The valve tappets (Figure 9.10)
will be removed when the
camshaft is removed. Intake and
exhaust valve tappets are iden-
tical. However, once a wear
pattern has been established,
the two parts should not be
interchanged.

VALVE SPRINGS:

Figure 9.11 — Valve Spring
VALVE SPRING FREE LENGTH
GN-190=1.910 inch (48.48 mm)
GN-191=2.074 inch (52.69 mm)
GN-220=2.074 inch (52.69 mm)
FORCE NEEDED TO COMPRESS SPRING
TO 1.39 INCH (35.2 mm)
GN-190 = 14.8-16.3 pounds (6.7-7.4kg)
GN-191 = 19.8-21.8 pounds (9.0-9.9kg)
GN-220 = 19.8-21.8 pounds (9.0-9.8kg)

INSTALLATION

After the valve train components have been properly
inspected and serviced, install the components as follows:
1. Install the intake and exhaust valves through the proper
valve guides in the cylinder head.
a. The exhaust valve has the smaller head.
b. The intake valve has the larger head.
c. Valve seat sizes will match their respective valve head sizes.
d. The exhaust valve stem is smaller than the intake valve stem.
Figure 9.12 — Compressing Valve Spring
34
Inspect the valve springs (Figure
9.11). Measure the spring FREE
LENGTH. Also measure the
spring length when a known
load is applied to the spring.