3.11
MAINTENANCE
CRANKSHAFT INDEXING
Polaris uses crankshafts that are pressed together. The
connecting rod journal center lines are indexed 180_(twins).
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 ar not limited to the following:
• Hydraulock 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
CHECKING CRANKSHAFT INDEX
1. Remove the drive belt, see DRIVE BELT in Chapter 7.
2. Remove the drive clutch, see “DRIVE CLUTCH
REMOVAL” on page 7.10.
3. 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.
4. 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 above.
5. Install a dial indicator into the magneto end cylinder spark
plug hole. The ignition timing is referenced by the
magneto end.
6. 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.
7. Continue to rotate the crankshaft in the normal direction of
rotation until the dial indicator reads .100" (2.54mm) after
top dead center (ATDC).
8. Bend the pointer or move the degree wheel until the
pointer aligns with a 180_ mark on the degree wheel.
9. 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.
10. Remove the dial indicator and install in PTO cylinder.
Repeat finding TDC. Note the degree wheel indication
when the dial indicator reads .100" ATDC. It should be
180_ (+/-2_) from the MAG cylinder mark.
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, piston holing)
• Excessive vibration of engine, back firing, etc.
• Rough idle, poor top speed.
CRANKSHAFT TRUING
Lubricate the bearings and clamp the crankshaft securely in
the holding fixture.If truing the crankshaft requires striking
with a hammer, always be sure to re-check previously
straightened areas to verify truing. Refer to the illustrations
below. Use Crankshaft alignment kit PN 2870569.
CAUTION
Disconnect the battery ground cable and ALL spark
plug high tension leads. Ground high tension leads to
the engine. Disconnect lanyard (if equipped) and/or
press the engine stop switch before proceeding with
the following procedure.
Dial Indicator
Degree
Wheel
.100 ATDC
Crankshaft center line
Dial Indicator
Degree
Wheel
.100 ATDC
MAG
PTO
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