Snowmobile Arctic Cat 2-Stroke (2007 year). Manual - part 15

2-46

AN151A

4. Inspect the crankshaft bearing area for wear. If any

wear is noted on either end, replace the crankshaft

end.

INSTALLING OUTER
CRANKSHAFT BEARINGS

„NOTE: On certain models, steps 1-3 are for
installing the MAG-side bearing.

1. Wrap a thick towel around the crankshaft; then

secure the crankshaft vertically in a vise.

2. Heat the bearing either by placing the entire bear-

ing in a pan of oil on a hot plate or by squirting oil

into the bearing and using a propane torch to heat

the inner race of the bearing until a slight smoke is

noted coming from the bearing.

3. Place any shims removed during disassembly onto

the crankshaft; then slide the bearing onto the

crankshaft making sure the dowel-pin hole in the

outer race is properly positioned and will align

with its hole and pin in the crankcase.

4. Slide the PTO-side bearing onto the PTO end mak-

ing sure the dowel-pin hole will align with the hole

and pin in the crankcase.

AN151A

REED VALVE ASSEMBLY

1. Inspect the reed valves, stoppers, and valve blocks

for cracks or any deterioration.

AQ046

2. Wash the reed valves, stopper, and cage assembly

in parts-cleaning solvent and blow dry.

3. Inspect the reed stopper height. Using a caliper,

measure the distance from the seat to the bottom

outer tip edge of the stopper. Measurement must

not exceed specifications. If measurement is not

within specifications, either bend or replace the

reed stopper.

AJ156

4. Inspect the reed-to-seat clearance. Using a feeler

gauge, measure the clearance. Clearance must be

less than 0.20 mm (0.008 in.). If clearance is not

within specifications, replace the reed valve.

5. To assemble, place the reed valves on the cage

with its clipped corner positioned to the lower

right hand corner of the cage. Place the reed stop-

per assembly into position and secure with the

three screws coated with red Loctite #271.

! CAUTION

DO NOT overheat the bearing.

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2

AQ047

Measuring Critical 

Components

„NOTE: Critical engine specifications charts can
be found at the beginning of this section.

CYLINDER HEAD VOLUME 
(Squish-Gap Method)

To check the squish gap, a micrometer and a heavy

piece of solder will be needed.

1. Remove the spark plugs from the engine.

2. Insert the solder piece down through the spark

plug hole and push it up against the inner cylinder

bore towards the MAG-side of the engine.

3. Pull the recoil rope and crank the engine over sev-

eral times while the solder is being held firmly in

place.

4. Remove the solder from the cylinder. Using the

micrometer, measure the very end of the squeezed

solder piece. Record the reading.

„NOTE: If the solder hasn’t been squeezed by the
piston, a larger piece of solder must be used.
Repeat procedure.

5. Using the opposite end of the solder piece, insert it

down through the spark plug hole towards the

PTO-side of the engine. Push on the solder until it

contacts the inner cylinder bore.

6. Pull the recoil rope and crank the engine over sev-

eral times. Remove the solder from the cylinder

and measure the squeezed end with a micrometer.

Record reading and refer to the chart.

„NOTE: Measure from PTO to MAG-side of the pis-
ton to accurately measure the squish gap. Never
measure across piston, exhaust to carburetor
side, as the piston will rock and the reading won’t
be accurate.

Readings may vary from side to side. Make sure the

smaller reading is within the specifications listed.

CYLINDER TRUENESS

1. Measure each cylinder in the three locations from

front to back and side to side for a total of six read-

ings.

MD2493

2. The trueness (out-of-roundness) is the difference

between the highest and lowest reading. Maxi-

mum trueness (out-of-roundness) must not exceed

specifications.

0725-586

PISTON SKIRT/CYLINDER 
CLEARANCE

1. Measure each cylinder front to back about 2.5 cm

(1 in.) from the bottom of each cylinder.

2. Measure the corresponding piston skirt diameter at a

point 1 cm (0.394 in.) above the piston skirt at a

right angle to the piston-pin bore. Subtract this mea-

surement from the measurement in step 1. The dif-

ference (clearance) must be within specifications.

2-48

AC091

PISTON-RING END GAP

1. Place each piston ring in the wear portion above

the exhaust port of its respective cylinder. Use the

piston to position each ring squarely in each cylin-

der.

2. Using a feeler gauge, measure each piston-ring

end gap. Acceptable ring end gap must be within

specifications.

MD2501

PISTON PIN AND PISTON-PIN BORE

1. Measure the piston pin diameter at each end and in

the center. Acceptable piston pin measurement

must be within specifications. If any measurement

varies by more than 0.02 mm (0.001 in.), the pis-

ton pin and bearing must be replaced as a set.

AN056

2. Insert a snap gauge into each piston-pin bore; then

remove the gauge and measure it with a microme-

ter. The diameter measurement must be within

specifications. Take two measurements to ensure

accuracy.

AC092

CONNECTING-ROD SMALL END 
BORE

1. Insert a snap gauge into each connecting-rod small

end bore; then remove the gauge and measure it

with a micrometer.

AN061

2. The diameter measurement must be within specifi-

cations.

CRANKSHAFT RUNOUT

1. Using the V Blocks (p/n 0644-022), support the

crankshaft on the surface plate.

„NOTE: The V blocks should support the crank-
shaft on the outer bearings.

2. Mount a dial indicator and base on the surface

plate. Position the indicator contact point against

the crankshaft location point F (PTO-end) from the

crankshaft end. Zero the indicator and rotate the

crankshaft slowly. Note the amount of crankshaft

runout (total indicator reading).

„NOTE: For runout location point specifications,
see Crankshaft Runout Specifications chart on
page 19 of this section.

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2

3. Position the indicator contact point against the

crankshaft location point D (MAG-end) from the

crankshaft end. Zero the indicator and rotate the

crankshaft slowly. Note the amount of crankshaft

runout (total indicator reading).

FC046

4. Position the indicator contact point against the

crankshaft at location point E (center). Zero the

indicator and rotate the crankshaft slowly. Note

the amount of crankshaft runout (total indicator

reading).

5. If runout exceeds specifications at any of the

checkpoints, the crankshaft must be either

straightened or replaced.

Assembling Engine

 

„NOTE: The use of new gaskets and seals is rec-
ommended when assembling the engine.

„NOTE: When the use of a lubricant is indicated,
use Arctic Cat 50:1 Injection Oil.

 1. Place the upper crankcase half (with its bottom

side up) on two blocks of wood.

2. Lightly grease the inner lips of the crankshaft

seals; then slide them onto the crankshaft.

3. Apply oil to the crankshaft bearings; then install

the crankshaft into the upper crankcase half. Be

sure the alignment hole in each bearing is posi-

tioned over its respective dowel pin in the crank-

case; then seat the crankshaft.

„NOTE: To check the bearing for proper position,
place the point of a sharp tool into the dimple
found in the bearing race. Strike the tool with the
palm of the hand in either direction. If the bearing
moves, it isn’t positioned correctly and must be
rotated until it drops onto the dowel pin. 

„NOTE: Make sure the crankshaft center C-ring
(integral with the center seal) is properly posi-
tioned in the groove of the upper crankcase half.

4. Install the four crankcase dowel pins.

5. Evenly apply a thin coat of Three Bond Sealant (p/n

0636-070) to the entire bottom half crankcase seal-

ing surface. 

„NOTE: Use only Three Bond Sealant (p/n 0636-
070) to seal the crankcase halves.

 MD0203

6. Install crankcase lower half. Install eight 8 mm

and four 6 mm cap screws. Tighten in three steps

the 8 mm cap screws to specifications and the 6

mm cap screws to specifications using the pattern

shown.

737-027A

! CAUTION

To prevent damage to the crankshaft, crankshaft
bearings, or seals, make sure to always lift the
crankshaft from both ends.

! CAUTION

If the bearings are not properly seated during
assembly, the crankcase halves will not seal tightly
and severe engine damage will result.