Valve Guide Replacement; Valve Lapping - Polaris 1999 Sportsman 400 Service Manual

118
6 . In s ta ll th e ret a in er on to p of th e va lve
s pring.
®
CAUTION
To
a void loss 0.( sp ring tension, do not
compress the spring allY more than
ncce, . . .
" w })'
(0
install the valve keepers.
CHAI' T ER FOUR
If
excess ive
valve stem- to-g uide clea rance is
f95\
pre sent, re place the va lve guides and valves. Entrust
~
va lve g uide replace me nt to a Polaris dea lersh ip or
q ua lified machine shop.
7. Compress the valve spring w ith a valve spring
compressor and install the valve keepers (Figure 84).
8. Wh en both va lve kee pers a rc in place, make sure
the y are seated aroun d the valve ste m (Fig u re 93 )
pri or to releas ing the co m press o r.
9. Slowl y release the tension fro m the co mpressor
and remo ve
it.
Afte r remo ving the co mpress or, in-
spect the va lve kee pers to make s ure they arc prop-
erly seated . Th en tap the end of the valve stem with
a so ft-faced ham mer. Th is w ill ens ure that the keep -
ers are properly se ated.
10. Rep eat Steps 1-9 fo r the rema ining va lves.
II. Install the cy linder head as described in thi s
chapter.
12. After installing the cy linde r head, adj ust the
valve cleara nce as descr ibed in C hapter T hre e.
Valve Gu ide Replacement
Valve Lap ping
Valve lap ping is a simple operation that can re-
store the va lve sea l wit hout ma chining
if
the amou nt
of wea r or distortion is not too great.
Perform this procedure after dete rmining that valve
scat
wi dth
and outside diameter arc within specifica-
tions. A lapping tool (Fi gure 94) is req uired.
I. Remove the valve as previously described in this
chapte r.
2. Ap ply a ligh t coating
otfine-grade
va lve lapping
compound on the seating surface of the valve.
3. Inser t the va lve into the cy linde r head.
4 . Wet the suction cup of the lappi ng too l and stick
it onto the head of the valve. Spin the stick in both
di rection s, wh ile pre ssing
it
aga inst the va lve sea t
and lap the valve to the seat . Eve ry 5 to 10 seco nds ,
rotate the va lve 180
0
in the va lve se al. Co ntinue
Valve keep ers
Valve st em - - - -""-
with this action until the mating surfaces on the
va lve and scat ar c smooth and eq ua l in size .
5. Closely exami ne the valve sea t in the cy linde r
hea
d. It
s hou ld be smooth and even wit h a smoo th,
po lis hed seati ng ri ng.
6. Repea t Steps 1-5 for the other valves.
7. Thorough ly clean the va lves and cy linde r head
in so lve nt or deterge nt and hot wa ter to remo ve all
va lve g rind ing compound. Dry thorou ghl y. Apply
a
light coating of e ng ine oil to a ll bare metal surfaces
to prevent rust.