Snowmobile Polaris PRO X (2003 year). Manual - part 20

ENGINE

2.48

Honing Procedure

Wash cylinder with solvent. Clamp cylinder securely in a soft jawed vise by the exhaust port 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 1/2I (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 1/2I (1.3 cm.) beyond the bore at the end of each stroke.
Release the hone at regular intervals to inspect bore size and finish. Do not “drag” the hone out of the bore.

Honing Procedure - Nicasil

Ni-Ca-Sil cylinders can be lightly honed if the proper stone is used. Ammco #3955 honing stones (for use with
the Ammco 3950 cylinder hone) are suitable and can be ordered through most automotive supply stores or VST.
See General Information chapter for tool ordering information.

Port Chamfering

Remove the sharp edges at the bottom and top of each port whenever boring or honing is performed. Make sure
there are no sharp edges.

IMPORTANT:

Cleaning the Cylinder After Honing

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

Crankcase Inspection / Bearing Fit

Any time crankshaft bearing failure occurs and the case is to be reused, Polaris recommends checking the bear-
ing fit into the case halves using the following procedure.

With case halves cleaned, press a replacement
bearing into each of the main bearing journals to
determine a basic amount of press fit. NOTE: Do a
comparison check of all journals by manually
forcing the bearing into the bearing seats noting if
any are noticeably loose or tight.

Normal hand

installation

will

indication

the

recommended interference fit. If the bearing falls
out of the case when the case is inverted, the case
should be replaced.

Crankshaft Main Bearing Inspection

Clean crankshaft thoroughly and oil main and connecting rod bearings with Polaris Premium 2 engine oil.
Carefully check each main bearing on the shaft.

NOTE: 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.

Crankcase Bearing Interference Fit:

C-3 - .0006

s (.015mm) - Crush

C-4 - .001

s (.025mm) - Crush

ENGINE

2.49

Connecting Rod (Big End) Bearing Inspection

Measure connecting rod big end side clearance with
a feeler gauge. Clearance should be equal on all
rods (within .002

s). Rotate rod on crankshaft and

check for 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.

NOTE: Specialized equipment and a sound knowledge
of crankshaft repair and straightening is required to per-
form crankshaft work safely and correctly. Crankshaft
repair should be performed by trained Polaris service
technicians in a properly equipped shop.

Piston Pin / Needle Bearing Inspection

Clean needle bearing in solvent and dry with
compressed air.

Inspect needle cage carefully for cracks or shiny
spots which indicate wear. Replace needle bearings
if worn or cracked, and always replace them if piston
damage has occurred.

Visually inspect piston pin for damage, discoloration,
or wear. Run your fingernail along the length of the
pin and replace it if any rough spots, galling or wear is
detected.

Connecting Rod Small End Inspection

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

Run your 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 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.

ENGINE

2.50

Crankshaft Truing

Lubricate the bearings and clamp the crankshaft securely in the holding fixture. On three cylinder crankshafts,
straighten one of the ends (Magneto or PTO) and then straighten the center section. Place the center section
in the holding fixture and then straighten the remaining end. If truing the crankshaft requires striking with a ham-
mer, always be sure to re-check previously straightened areas to verify truing. Refer to the illustrations below.

Crankshaft Runout Inspection

When checking the crankshaft runout, it is important to
measure with a dial indicator in the correct position.

When measuring on the flywheel side:

SMeasure runout 1/2” (12.7mm) from the bearing flat.

When measuring from the PTO side:

SMeasure runout where the taper starts after the
bearing flat.

Refer to the illustrations. Acceptable crankshaft
runout is .000--.004” (0--.10mm) for all Polaris
crankshafts.

1/2” (12.7mm)

Flywheel (MAG) side

Measure where taper starts

PTO Side

Crankshaft Alignment Fixture

PN 2870569

ENGINE

2.51

Crankshaft Truing

NOTE: The rod pin position in relation to the dial indi-
cator position tells you what action is required to
straighten the shaft.

To correct a situation like the one shown in the
illustration at right, strike the shaft at point A with a
brass hammer.

NOTE: The rod pin position in relation to the dial indi-
cator position tells you what action is required to
straighten the shaft.

To correct a situation like the one shown in the
illustration at right, squeeze the crankshaft at
point A. (Use tool from alignment kit).

If the crank rod pin location is 180_ from the dial
indicator (opposite that shown above), it will be
necessary to spread the crankshaft at the A
position as shown in the illustration at right. When
rebuilding

and

straightening

crankshaft,

straightness is of utmost importance.

Runout

must be as close to zero as possible.

NOTE: Maximum allowable runout is .004I (.1 mm).

HIGH .004 (.1mm)

SUPPORT CRANKSHAFT
AT THESE TWO BEARINGS

HIGH .002 (.05mm)

HIGH .005 (.13mm)

HIGH .002 (.05mm)

HIGH .005 (.13mm)

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