Engine / Cooling
3.58
Crankshaft Indexing -- 1200cc Carbureted Engin es
Polaris Watercraft crankshafts are pressed together or
(indexed) so the connecting rod journal center lines are
120° apart from each other.
It is sometimes necessary to check multi-cylinder crank-
shafts 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; See Troubleshoot-
ing, Chapter 2.
S Impact to impeller from foreign object or acci-
dent;
S Abrupt piston or other mechanical 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 proceed-
ing with the following steps.
1. Securely fasten a degree wheel on the flywheel or
output coupler/driveshaft. Use a large degree wheel
for more accuracy, and make sure it is mounted
concentrically with the crankshaft center line. Cut a
slot in a paper or cardboard degree wheel and slide it
over the driveshaft if engine and pump shaft is
installed in craft. Again, be sure to secure the degree
wheel.
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 flywheel or drive coupler mounted 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 (counter
clockwise as viewed from the rear of the craft) until the dial indicator reads .100² (2.54mm) after top dead
center (ATDC). IMPORTANT: Do not allow the crankshaft to move from this position.
6. Bend the pointer or move the degree wheel until the pointer aligns with the 120° 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 120° mark
when the dial indicator reads .100² (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 (center). Repeat steps 4 and 5 for cylinder # 2. Note the
degree wheel indication when the dial indicator reads .100² ATDC. It should be 120° (± 2°) from cylinder #1.
Proceed to PTO cylinder (#3). Cylinder #3 should also be 120°(± 2°) 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
120°
Three Cylinder
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