Polaris 2012 Sportsman Forest 500 International, Service Manual

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3.26
ENGINE
9923412 - 2012 Sportsman 400/500 and EFI Tractor Service Manual
© Copyright 2011 Polaris Sales Inc.
NOTE: If valve guides are replaced, valve seats must
be reconditioned. Refer to the “Valve Seat
Reconditioning” procedure.
Combustion Chamber
Clean all accumulated carbon deposits from combustion
chamber and valve seat area with a soft wire brush.
Valve Seat Reconditioning
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.
Cylinder Head Reconditioning
NOTE: Servicing the valve guides and valve seats
requires special tools and a thorough knowledge of
reconditioning techniques. Follow the instructions
provided in the cylinder head service tool kit.
Valve Guide Removal / Installation
1. Remove all carbon deposits from the combustion
chamber, valve seat and valve guide area before
attempting to remove valve guides.
CAUTION:
Carbon deposits are extremely abrasive and may
damage the valve guide bore when guides are
removed.
2. Place new valve guides in a freezer for at least 15
minutes while heating cylinder head.
3. Heat cylinder head in an oven or use a hot plate to
bring cylinder head temperature to 212° F (100° C).

CAUTION: Do not use a torch to heat cylinder head
or warpage may result from uneven heating. Head
temperature can be checked with a pyrometer or a
welding temperature stick.
Follow the manufacturer’s instructions provided with the
valve seat cutters in commercially available valve seat
reconditioning kits. Abrasive stone seat reconditioning
equipment can also be used. Keep all valves in order with
their respective seat.
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.
4. When thoroughly heated, place cylinder head on blocks of
wood which will allow the old guides to be removed.
5. 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.
6. Place cylinder head on cylinder head table.
NOTE: Be sure cylinder head is still at 212° F
(100° C) before installing new guides.
CAUTION
Wear eye protection when performing cylinder
head service. Valve guide replacement will
require heating of the cylinder head.
Wear gloves to prevent burns.
Too Uneven Good Too
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