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9926806 R03 - 2015 - 2016 RANGER ETX / 570 2-SEAT 2015 - 2016 RANGER 570 CREW Service Manual
© Copyright Polaris Industries Inc.
3.53
VALVE SEAT RECONDITIONING
Valve seat reconditioning should be performed by a
technician proficient in cylinder head reconditioning
techniques. Reconditioning techniques vary, so follow
the instructions provided by the valve reconditioning
equipment manufacturer. Do not grind seats more than
necessary to provide proper seat surface, width, and
contact point on valve face.
CAUTION
Wear eye protection or a face shield during cylinder
head disassembly and reassembly.
Valve Seat Inspection
Inspect valve seat in cylinder head for pitting, burnt
spots, roughness, and uneven surface. If any of the
above conditions exist, the valve seat must be
reconditioned. If the valve seat is cracked the cylinder
head must be replaced.
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.
Renewing Valve Seats
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.
NOTE
Remove only the amount of material necessary to
repair the seat surface.
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.
ENGINE / COOLING SYSTEM
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