Polaris 2005 SPORTSMAN 500 Servise Manual page 84

ENGINE
Too
Uneven
Wide
NOTE: Valve seat width and point of contact on the
valve face is very important for proper sealing. The
valve must contact the valve seat over the entire
circumference of the seat, and the seat must be the
proper width all the way around. If the seat is uneven,
compression leakage will result. If the seat is too
wide, seat pressure is reduced, causing carbon
accumulation and possible compression loss. If the
seat is too narrow, heat transfer from valve to seat is
reduced and the valve may overheat and warp,
resulting in burnt valves.
1. When thoroughly heated, place cylinder head on
blocks of wood which will allow the old guides to
be removed.
2. Using valve guide driver, drive guides out of the
cylinder head from the combustion chamber side.
Be careful not to damage guide bore or valve seat
when removing guides.
3. Place cylinder head on cylinder head table.
NOTE: Be sure cylinder head is still at 212° F
(100° C) before installing new guides.
A
Valve Guide Installed Height
Valve Guide Height:
.689-.709I (17.5-18.0 mm)
4. Place a new guide in the valve guide installation
tool and press guide in to proper depth. Check
height of each guide above the cylinder head (A).
NOTE: The guide can also be driven in to the
proper depth. Inspect the guide closely for cracks
or damage if a driver is used.
3.24
Too
Good
Narrow
Reaming The Valve Guide
5. Allow cylinder head to cool to room temperature.
Apply cutting oil to the reamer. Guides should be
reamed from the valve spring side of the cylinder
head. Ream each guide to size by turning the
reamer clockwise continually. Continue to rotate
reamer clockwise during removal of the tool.
6. Clean guides thoroughly with hot soapy water and
a nylon brush. Rinse and dry with compressed
air. Apply clean engine oil to guides.
7. Install pilot into valve guide.
8. Apply cutting oil to valve seat and cutter.
9. Place 46° cutter on the pilot and make a light cut.
10. Inspect the cut area of the seat.
If the contact area is less than 75% of the
S
circumference of the seat, rotate the pilot
180° and make another light cut.
If the cutter now contacts the uncut
S
portion of the seat, check the pilot. Look
for burrs, nicks, or runout. If the pilot is
bent it must be replaced.