ENGINE
2.52
Crankshaft Indexing
Polaris crankshafts are pressed together or ‘‘indexed” so the connecting rod journal center lines are 180q (twins)
or 120q (triples) 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 or cylinders. Causes for out-of-index crankshafts include but are not not
limited to:
S Hydrolock from water or fuel;
S Impact to drive clutch from foreign object or accident;
S Abrupt piston or other mechanical failure;
S Engine lock-up due to drive belt failure;
Following is a method of checking:
CAUTION:
Disconnect battery ground cable and all spark plug high tension leads; ground high tension leads to engine. Dis-
connect lanyard from engine stop switch before proceeding with the following steps.
1. Securely fasten a degree wheel on the flywheel or
PTO end of crankshaft. Use a large degree wheel for
more accuracy, and make sure it is mounted
concentrically with the crankshaft center line.
2. Sharpen a coat hanger or section of welding rod and
anchor it to a convenient spot. Point the sharpened
end at the outer perimeter of the degree wheel.
3. Install a dial indicator into the magneto end cylinder
spark plug hole (front) (#1). (The ignition timing is
referenced by the magneto end.)
4. Rotate the engine to bring the piston to top dead
center (TDC) on the cylinder with the indicator
installed.
5. Locate TDC as accurately as possible by finding the
center of the point where there is no piston
movement. ‘‘Zero” the dial indicator at this point.
Continue to rotate the crankshaft in the normal
direction of rotation until the dial indicator reads .100s
(2.54mm) after top dead center (ATDC).
IMPORTANT: Do not allow the crankshaft to move
from this position.
Crankshaft Indexing (Continued)
6. Bend the pointer or move the degree wheel until the pointer aligns with the 180q or 120q mark on the degree
wheel.
7. 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 by repeating steps 4. and 5. . The pointer should align with the
180q or 120q mark when the dial indicator reads .100s (2.54mm) ATDC.
IMPORTANT:
Do not
move the degree wheel or pointer after the initial setting on the mag end cylinder - simply
read the wheel and dial indicator.
8. Remove the dial indicator and install in cylinder #2 or center cylinder. Repeat steps 4. and 5. Note the degree
wheel indication when the dial indicator reads .100s ATDC. It should be 180q or 120q (r 2q) from cylinder #1.
Repeat procedure on PTO cylinder (#3) where applicable. Cylinder #3 should also be 120q¢r 2q) from cylinder
#1.
Symptoms of an out of index crankshaft can include:
S Difficulty calibrating carburetor (repetitive plug fouling on one cylinder with no other cause);
S Unexplained piston failure on one cylinder (i.e. severe detonation, broken ring lands, piston holing);
S Excessive vibration of engine, backfiring, etc.;
S Rough idle, poor top speed.
Dial Indicator
Degree
Wheel
.100 ATDC
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