Valve Seat Reconditioning - Polaris PREDATOR 50 2009 Manual

5. Install the valve in its mating guide and lift it 5mm off of
the seat. Push valve back and forth and measure deflection
in two directions. If deflection exceeds limit repeat test with
a new valve, or measure stem to guide clearance as outlined
in Step 6 and 7 to determine if wear is in the guide or the
valve stem (or both).
6. Measure diameter of valve stem with a micrometer in three
places and in two different directions (six measurements
total). Replace if excessive wear is evident.
7. Measure valve guide inside diameter at the top middle and
end of the guide using a small hole gauge and a micrometer.
Measure in two directions, front to back and side to side.
8. Subtract valve stem measurement to obtain stem to guide
clearance. NOTE: Be sure to measure each guide and valve
combination individually.
9. Replace valve and/or guide if clearance or deflection is
excessive.
NOTE: If valve guides are replaced, valve seats must
be reconditioned.
ENGINE / TRANSMISSION

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.
Too
Uneven
Wide
Cylinder Head Reconditioning
NOTE: Servicing the valve guides and valve seats
requires special tools and a thorough knowledge of
cylinder head reconditioning
following is an outline of general reconditioning
techniques. Follow specific seat cutting instructions
provided by the manufacturer of the seat cutting
equipment. Abrasive stone seat reconditioning
equipment can also be used. Keep valves in order
with their respective seat. Do not attempt cylinder
head service without the proper tools or knowledge
of cylinder head service.
CAUTION
Wear eye protection when performing cylinder
head service. Valve guide replacement will
require heating of the cylinder head.
gloves to prevent burns.
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.
Good Too
Narrow
techniques. The
Wear
3.19
3