Combustion Chamber; Valve Guide Removal / Installation; Valve Seat Reconditioning - Polaris Sportsman 850 Service Manual

ENGINE / COOLING SYSTEM

COMBUSTION CHAMBER

1. Clean all accumulated
combustion chamber and valve seat area.
Carbon Clean Fuel Treatment (2871326) can be used
to help remove carbon deposits.
IMPORTANT
Do not use a metal scraper, a coarse wire brush, or
abrasive cleaners to clean the cylinder head. Damage
may result.
2. Visually inspect cylinder head gasket surface and
combustion chamber for cracks or damage. Pay
close attention to the areas around spark plug and
valve seats.

VALVE GUIDE REMOVAL / INSTALLATION

1. Support cylinder head and place valve guide
remover into valve guide from the combustion
chamber side.
2. Drive or press old valve guides out of cylinder head.
CAUTION
Replacement of valve guides requires an oven, special
equipment and experience to do the job correctly. If you
are unsure of your ability to do the repair professionally
it is best to sublet the labor to a competent machinist.
Valve seat reconditioning is required when valve guides
are replaced.
CAUTION
The cylinder head can be easily damaged if the
procedure is done carelessly.
3. Apply 90 weight oil to outside of new valve guides.
3.52
carbon deposits
NOTE
4. Drive or press new guides from camshaft side of
head to proper installed height. Note difference
from
between intake and exhaust guide height:
Intake Valve Guide Height
Exhaust Valve Guide Height
5. Ream or hone new valve guides to size to obtain
specified stem-to-guide clearance. Ream from
combustion chamber side of head.
Do not tilt the reamer while reaming the guide. Always
rotate the reamer in a clockwise direction.
6. Clean cylinder head thoroughly with clean solvent.
7. Inspect valve seats and recondition if necessary.

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.
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,
MEASUREMENT
9.18 mm ± 0.25 mm
MEASUREMENT
7.00 mm ± 0.25 mm
CAUTION