Polaris Sportsman XP 1000 S 2020 Service Manual page 182

ENGINE / COOLING SYSTEM
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. The valve may overheat and warp,
resulting in burnt valves.
1. Install pilot into valve guide.
2. Apply cutting oil to valve seat and cutter.
3. Place 46° cutter on the pilot and make a light cut.
4. Inspect the cut area of the seat:
• If the contact area is less than 75% of the
circumference of the seat, rotate the pilot 180° and
make another light cut.
• If the cutter now contacts the uncut portion of the seat,
check the pilot. Look for burrs, nicks, or runout. If the
pilot is bent it must be replaced.
• If the contact area of the cutter is in the same place,
the valve guide is distorted from improper installation.
• If the contact area of the initial cut is greater than 75%,
continue to cut the seat until all pits are removed and a
new seat surface is evident.
NOTICE
Remove only the amount of material necessary to
repair the seat surface.
3.52
5. To check the contact area of the seat on the valve
face, apply a thin coating of Prussian Blue paste to
the valve seat. If using an interference angle (46°)
apply black permanent marker to the entire valve
face (A).
6. Insert valve into guide and tap valve lightly into place
a few times.
9931493 R03 - 2020-2021 Sportsman XP 1000 S Service Manual
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