Reface Valves And Seats - Generac Power Systems GTV99O Service Manual

SECTION 5: CYLINDER HEAD AND VALvEs
INSPEO AND REPAIR
I Check cylinder head (Figure 5-7). Be sure allgasket mate_
rialis rernoved from sudaces before checking. Use d gasKer
scraper f necessary
a.Inspect cylinder head for.r€cks or damage.
b. Use a sudace plate or straightedge
and check q inderhead
mounUng sudace for distortion.
lf mounting surfaces are distoned more than .004" (0.1
mm), the cylnder head nrust be replaced.
Note: lt is not fecommended that cytinder heao moun.-
ing surtaes be rcsuiaced.
Figute 5-7. check Cytindet Head Distottion
2. Clean thevalve gu des and measurethe r l.D. lsing a sptit
ball bore gauge (Figure 5,8)
a. Replace head if either valve guide measures 7.06 mm
(0.278 in.) or more.
REFACE VALVES
AND SEATS:
1. Va lve seats may be reconditioned using a valve seai cutter
lf valve seat k widerthan dimensjon shown in Figure 5-9, a
narrcwing cutter should be used to ensure that conEcr area
of valve seat is centered on face of valve (Figure 5-tO)
a. use a 60" cutter to narrow seat from bottom and a i5.
cutterto narrow seat from top (Figure 5-9).
Note: fi valve seat is loose or uacked, rcpla.e cytinder
60'CUTTEF
1 5 ' C U T T E R
Figurc 5-9. Valve Seat Dinensions
2. Valve faces may be resudaced to 45.. See Figure 5_10 for
diraensions ior valves.
3. Lap valves and seats with a valve lapping toot ano valve
lapping compound.
Note: ln most instances it is morc economi.at to reptace
the valves than to refa@ them,
r
T
Figute 5-10. Valve Dinensions
4. Measure valve stem diarneier at specified distance frcm end
ofvalve, as shown n Figure 5 11.
Replace if less than 6_9 mm (0.272 inchet, or if total cleaF
ance between valve stem and valve gu de exceeds O_12 mnr
(0.0047 in)
Figwe 5-8. Check valve guides
5 3