Snowmobile Polaris IQ (2007-2008 year). Manual - part 32

5.6

Engine and Cooling Systems

Piston Inspection

Check piston for scoring or cracks in piston crown or pin
area. Excessive carbon buildup below the ring lands is an
indication of piston, ring or cylinder wear. On Fuji engines,
measure piston outside diameter at a point that is 1/2

(12.7mm) up form the bottom of the skirt at a 90

angle to

the direction of the piston pin.

Subtract this measurement from the minimum cylinder
measurement (90

to the pin). If clearance exceeds the

service limit, the cylinder should be re-bored (replaced if
Nicasil-lined) and new pistons and rings installed.

Piston Ring Installed Gap

Position the ring 1/2

(1.3 cm) from the top of the cylinder

using the piston to push it squarely into place. Measure
installed gap with a feeler gauge at both the top and
bottom of the cylinder.

NOTE: A difference in end gap indicates cylinder
taper. The cylinder should be measured for
excessive taper and out-of-round. Replace rings if
the installed end gap exceeds the service limit.
Always check piston ring installed gap after re-
boring a cylinder or when installing new rings.

Piston rings are installed with marking or beveled side up.

Reed Valve Inspection

Loosen he hose clamps

Remove the carburetor or the throttle body from the intake
boots.

Remove the intake boot fasteners and hose holders (if
applicable).

Remove the intake assembly.

Separate the intake boot(s) from the reed cage.

Separate the reed stuffer(s) from the reed cage and inspect
the reeds before they are removed from the reed cage.

NOTE: Measure the air gap between the fiber reed and
the reed block. The air gap should not exceed .015"
(.38mm). If clearance is excessive DO NOT attempt to
reverse the reeds to reduce the air gap. Always replace
them if damaged or worn. Check each fiber reed for white
stress marks or missing material.

If damaged remove and replace the reeds on the reed cage.

Bearing Fit

Any time crankshaft bearing failure occurs and the case is
reused, check the bearing fit into the case halves using the
following procedure.

With case halves cleaned, reinstall the main bearings with
a piece of Plastigage between the bearing race and
crankcase.

Install and torque the crankcase fasteners to specifica-
tion. Take the crankcase apart, and then measure the
Plastigage. Compare Plastigage width to interference fit

The air gap should not exceed .015” (.30mm)

5.7

Engine and Cooling Systems

specification.

Main Bearing

Clean crankshaft thoroughly and oil main and connecting
rod bearings with Polaris engine oil. Carefully check each
main bearing on the crankshaft.

Due to extremely close tolerances, the bearings must be
inspected visually and by feel. Look for signs of
discoloration, scoring or galling. Turn the outer race of
each bearing. The bearings should turn smoothly and
quietly. The inner race of each bearing should fit tightly on
the crankshaft. The outer race should be firm with minimal
side to side movement and no detectable up and down
movement. Replace any loose or rough bearings.

Connecting Rod Lower Bearing

Measure connecting rod big end side clearance with a
feeler gauge on both sides of the connecting rod. The side
clearance on either side of the connecting rod cannot
exceed the connecting rod side clearance specification.
The difference between the two clearance measurements

cannot exceed the maximum clearance differential
specification.

Rotate the connecting rod on the crankshaft and feel for
any rough spots. Check radial end play in rod by
supporting rod against one thrust washer and alternately
applying up and down pressure. Replace bearing, pin, and
thrust washers if side clearance is excessive or if there is
any up and down movement detectable in the big end
bearing.

Piston Needle Bearing

Clean the end of the connecting rod and inspect inner bore
with a magnifying glass. Look for any surface
irregularities including pitting, wear, or dents.

Run a fingernail around the inside of the rod and check for
rough spots, galling, or wear.

Oil and install needle bearing and pin in connecting rod.

Rotate pin slowly and check for rough spots or any
resistance to movement.

Slide pin back and forth through bearing while rotating and

= In. / mm.

.061mm)

Bearing Interference Fit:
Carbureted = .001

-.002

(.026 -.051mm)

CFI = .0014

- .0024

(.061mm)

= In. / mm.

Connecting Rod Side Clearance:
.0114

-.0295

(.289-.749mm)

Maximum Clearance Differential
.002

(.051mm)

5.8

Engine and Cooling Systems

check for rough spots.

With pin and bearing centered in rod, twist ends back and
forth in all directions to check for excessive axial play.

Pull up and down evenly on both ends of pin to check for
radial play.

Replace pin and bearing if there is any resistance to rotation
or excessive axial or radial movement. If play or roughness
is evident with a new pin and bearing, replace the
connecting rod.

Crankshaft Index

Polaris crankshafts are pressed together. The connecting
rod journal center lines are indexed 180

apart from each

other.

It is sometimes necessary to check multi-cylinder
crankshafts to verify that one cylinder has not been forced
out of position relative to the other cylinder. Some causes
for a “out of index” crankshaft include but are not limited to
the following:

• Hydrolock from water or fuel

• Impact to drive clutch from object or accident

• Abrupt piston or other mechanical failure

• Engine lock-up due to drive belt failure

Symptoms of an out of index crankshaft can include but
are not limited to the following:

• Difficulty calibrating carburetor (repetitive plug fouling

on one cylinder with no other cause)

• Unexplained piston failure on one cylinder (i.e. severe

detonation, broken ring lands, etc.)

• Excessive vibration of engine, back-firing, etc.

• Rough idle, poor top speed.

Checking Crankshaft Index

Remove the drive belt and drive clutch.

Securely fasten a large degree wheel on the flywheel or
PTO end of the crankshaft. Make sure that it is mounted
concentrically with the crankshaft center line.

With a section of wire (wire coat hanger), anchor it to a
convenient spot. Bend one end at the outer perimeter of the
degree wheel as shown below.

Install a dial indicator into the magneto end cylinder spark
plug hole. The ignition timing is referenced by the magneto
end.

Locate TDC as accurately as possible by finding the center
of the point where there is no piston movement note the
“Zero” the dial indicator at this point.

Continue to rotate the crankshaft in the normal direction of
rotation until the dial indicator reads .100" (2.54mm) after
top dead center (ATDC).

Bend the pointer or move the degree wheel until the pointer
aligns with a 180° mark on the degree wheel.

With the pointer aligned, make sure the degree wheel and
pointer are secured and will not move out of position. Re-
check accuracy of this location a few times. The pointer
should align with the 180° mark when the dial indicator
reads .100” (2.54mm) ATDC.

NOTE: Do not move the crankshaft, degree wheel or
pointer after the initial setting on the MAG end
cylinder - simply read the wheel and dial indicator.

Remove the dial indicator and install in PTO cylinder.
Repeat finding TDC process. Note the degree wheel
indication when the dial indicator reads .100" ATDC. It
should be 180° (+/-2°) from the MAG cylinder mark.

5.9

Engine and Cooling Systems

Cylinder Honing

The cylinder bore must be de-glazed whenever new pis-
ton rings are installed. A light honing with fine stones re-
moves only a very small amount of material. A proper
crosshatch pattern is important to provide a surface that
will hold oil, and allow the rings to seat properly. If the
crosshatch is too steep, oil retention will be reduced. A
crosshatch angle which is too shallow will cause ring vi-
bration, poor sealing, and overheating of the rings due to
blow-by and reduced contact with the cylinder wall. Ser-
vice life of the pistons and rings will be greatly reduced.
NOTE: A Nicasil cylinder can be lightly honed with a
soft stone hone but an not be oversized.

Honing Procedure

Wash the cylinder with cleaning solvent.

Clamp the cylinder in a soft jawed vise by the cylinder
studs.

Place hone in cylinder and tighten stone adjusting knob

until stone contacts the cylinder walls (DO NOT
OVERTIGHTEN). Cylinders may be wet or dry honed
depending on the hone manufacturer's recommendations.
Wet honing removes more material faster and leaves a more
distinct pattern in the bore. Using a .50" (13 mm) drill motor
rotating at a speed of 300-500 RPM, run the hone in and
out of the cylinder rapidly until cutting tension decreases.
Remember to keep the hone drive shaft centered to prevent
edge loading and always bring the stone approximately .5"
(1.2 cm) beyond the bore at the end of each stroke.

Release the hone at regular intervals to inspect bore size and
finish.

Cleaning The Cylinder After Honing

It is very important that the cylinder be thoroughly cleaned
after honing to remove all grit material. Wash the cylinder
in a solvent, then in hot soapy water. Pay close attention
to areas where the cylinder sleeve meets the aluminum
casting (transfer port area). Use electrical contact cleaner
if necessary to clean these areas. Rinse thoroughly, dry
with compressed air, and oil the bore immediately with
Polaris Premium 2 Cycle Lubricant.

NOTE: Always check piston to cylinder clearance
and piston ring installed gap after honing or boring
is complete.

EXAMPLE OF A CROSS HATCH PATTERN

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