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9850064 R03 - 2021 650 / 850 Matryx Trail Performance / Crossover Snowmobile Service Manual
© Copyright Polaris Inc.
CRANKSHAFT RUNOUT INSPECTION
The Crankshaft must be true for optimal performance
and engine longevity. Use the procedure bellow to
measure Crankshaft runout.
1. Support the crankshaft in a set of “V” blocks as
shown.
2. Use a dial indicator to measure the runout at the
following locations:
• PTO end = First taper after bearing flat.
• MAG end = 1/2" from bearing flat.
3. Compare the crankshaft runout measurements to the
specification limit. Runout deflection cannot exceed
the specification limit. If the runout exceeds the
maximum specification, crankshaft truing may correct
the deflection.
MEASUREMENT
Crankshaft Runout Limit:
0.0025 in (0.030 mm)
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.
Symptoms of an out of index crankshaft can include but
are not limited to the following:
• 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
Some causes for an “out of index” crankshaft include but
are not limited to the following:
• Hydrolock from water or fuel
• Impact(s) to the drive clutch from an object or accident
• Abrupt piston or other mechanical failure
• Engine lock-up due to drive belt failure
