SCORPION 1975 Brut User manual

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1975
Scorpion
Brut
Service Manual
Engine Section
1-l

SERVICE MANUAL· 1975 SCORPION BRUT
ENGINE SYSTEM
General Description:
The Scorpion Brut en gine is especially designed
and built for today's high performance
snowmobile.
Any internal combusion engine performs best
and is most reliable at a constant operating tem-
perature. The Scorpion Brut engine is ther -
mostatically controlled to run at a 180 degree+4
degree F cylinder head temperature whether the
outside temperature is -30 degree F or +50
degree F. This close temperature control reduces
to a minimal, the necessity of changing spark
plugs and the worry of piston seizing.
However, in order to get the best possible use
and ensure that it retains its high degree of
dependability, performance and endurance, it
must receive proper care and maintenance.
Therefore, it is necessary to know something
about the basic fundamentals of this engine and
how it functions .
OPERATION
The Scorpion Brut engine uses a mixture of
gasoline, oil and air for combustion, lubrication
and cooling . It fires on every strok e of each
piston. There are two or three power strokes
(depending on the model), for every revolution of
the crankshaft.
As the piston moves upward in the cylinder, it
draws the fuel/air mixture into the crankcase
through the intake manifold while at the same
time compressing fuel that has been forced into
the combustion chamber (Fig. 1-1 A).
As the piston nears top dead center, the spark
plug is fired and the compressed fuel/air mixture
burns and expands, thereby forcing the piston
downward on a power stroke.
As the downward stroke of the piston turns the
crankshaft, it al so starts to compress the fuel/air
mixture in the crankcase and, simultaneously,
opens the exhaust po rt and closes the intake por t
(Fig. 1-1 B & C).
1-2
)

After the exhaust port is fully open and the intake
port is fully closed, further piston travel starts to
open the transfer ports. The compressed fuel/air
mixture from the crankcase th en travels up the
transfer ports and into the combustion area.
After most of the burned exhaust gases have left
the cylinder, an incoming charge of fuel/air mix -
ture scavenges the combustion area giving it a
fresh charge and the cycle is then repeated. (Fig.
1-lD).
Because lubrication is dependent on the mixing of
oil and fuel, it is extreme ly important that good
quality oil and gasoline are properly mixed. The
proper ratio of oil to gasoline will prevent
possible engine overheating, piston or cy lind er
scoring, or eventua l engine seizure. Too much oil
and not enough gasoline can lead to incomplete
combustion, fouled pl'-'gs, carbon build-up and
muffler clogging.
SERVICE MANUAL · 1975 SCORPION BRUT
INTAKE
EXH/UST
TRANSFER
FIG. 1-1
1·3

SERVICE MANUAL · 1975 SCORPION BRUT
TABLE OF SPECIFICATIONS
IDENTIFICATION
SIZE TORQUE
Cylinder H ead Nuts
8mm 20Ft. lbs.
Cylinder Base Nuts 10 mm
25Ft. lbs.
Flywheel Nut 45 - 50 Ft. lbs.
Intake Manifold Nuts 8mm
20Ft. lbs.
Exhaust Manifold Nuts 8mm 20Ft. lbs .
Wat er Manifold Nuts 6mm
15Ft. lbs.
Crankcase Bolts
8mm 20Ft. lbs.
10
mm 25Ft. lbs.
CRANKCASE BOLTS TORQUE SEQUENCE
•
20
10 mm Bolts Circled
• • • • • • • •
15 11 7 3 1 6
10
14
All others are
e18
16
•
17
13 9 5 2 4 8
12
• • • •
19
••
• • •
•
440 Brut is shown. Use the same torquing pattern for the 340 Brut which has
12
instead of 18 - 8 mm bolts.
CYLINDER HEAD NUT TORQUING SEQUENCE:
340, 440 Models
1-4
® (1)

(
ENGINE REMOVAL
1. Separate the carburetors from
the engine by removing the
clamps which secure the rubber
connectors to the carburetor
outlet.
2. Remove the 3/8" nuts which
fasten the tie rod ends to the
steering frog.
Remove the cotter key from the
lower end of the steering frog.
Remove the 2lf4" bolts which
secure the upper steering brack-
et to the roll bar.
SERVICE MANUAL· 1975 SCORPION BRUT
CLAMPS
FIG. 1·2
CARB. ELBOW MOUNTING SCREWS
FIG. 1·3
STEERING FROG
TIE RODS
l-5

SERVICE MANUAL· 1975 SCORPION BRUT
f
Lift the steering post clear of the
engine area.
UPPER STEERING BRACKET
/
3. Disconnect the engine electrical
connectors, spark plug leads and
the temperature light wire from
th heat sensing element.
SENSING ELEMENT----+-----=
CONNECTOR
1·6
FIG. 1·4
FIG. 1-5
FIG. 1-6

(
4. Disconnect the coolant hoses
from the manifolds and plug both
manifolds and hoses to reduce
coolant spillage.
COOLANT BY·
PASS HOSE
SERVICE MANUAL· 1975 SCORPION BRUT
FIG. 1-7
FIG. 1·8
HOSE---I
1-7

SERVICE MANUAL· 1975 SCORPION BRUT
5. Remove 2-7 /16" lock nuts which
secure the front motor mounts to
the chassis.
Remove the 6 - 8 mm screws
which secure the rear motor
mounts to the engine.
6. Release the springs which fasten
the exhaust wye to the muffler .
7. lift the engine from the s led and
drain the coolant.
ENGINE DISASSEMBLYI
ASSEMBLY
Disassembly (Peripheral Equipment)
1. Remove the carburetor to engine
Elbow connectors. (2 socket head
screws/elbow) See Fig . 1- 2.
2. Disconnect the exhaust wye
(Socket head screws).
3. Disconnect the coolant by - pass
hose. (2 clamps). See Fig. 1-7.
l -8
. ,,
FIG. 1-10

4. Remove the coolant inlet and
outlet manifolds. (6 mm nuts).
5. Disconnect the water pump
mounting brackets. (3 - 8 mm
bolts).
6. R emove the front motor mounts
from the engine.
SERVICE MANUAL· 1975 SCORPION BRUT
COO~ANT
COOLANT
INLET MANIFOLD
OUTLET
MANIFOLD
FIG. 1-12
FIG. 1-13
1-9

SERVICE MANUAL· 1975 SCORPION BRUT
Engine Disassembly
1. Remove heads.
Remove 8 mm nuts (6 per head).
Pry up carefully to separate
heads from cylinder.
2. Remove cylinders.
].] 0
Remove 10 mm cylinder nuts.
Slide cylinders off pistons.
FIG. 1-14
~--- HEAD NUTS
FIG. 1-15
CYLINDER NUTS

3.
(
(
Remove pistons.
Extricate snap ring with snap ring
pliers.
SNAP RIN
Slide piston pin out of piston.
Exercise care that excessive side
pressure is NOT applied to the
connecting rod.
Pull piston from connecting rod.
Remove pin bearing and bearing
spacers.
SERVICE MANUAL- 1975 SCORPION BRUT
FIG. 1-16
FIG. 1-17
FIG. 1-18
1-1 1

SERVICE MANUAL -1975 SCORPION BRUT
PTO END
1. Remove hex h ead bolts with
locking s trips.
2. Remove seal.
3. Remove ga ske t.
MAGNETO END
1. Remove Recoil Start er. Tak e h ex
head screws out. Pull recoil off
crankcase.
2. Complete Disa sse mbly.
1-12
LOCKING STRIP - - --- ----1~
~'
)
FIG. 1-19
)
HEX SCREWS
t
FIG. 1-20

340MODEL
a. Remove pump pulley bolts, eme rgen-
cy rope pulley and water pump pulley.
SERVICE MANUAL • 1975 SCORPION BRUT
440MODEL
a. Remove 6 mm pump pulley bolts,
emergency rope pulley and water
pump pulley.
EMERGENCY ROPE PULLEY----,?'. .,...> ' '"--------- ,., -. -- k + ·~ . ~
'*
WATER PUMP PU
b. Remove 18 mm nut holding rotor on
shaft.
FIG. 1-22
FIG. 1-21
b. Remove 18 mm nut holding rotor on
shaft.
FIG. 1-23
l-1 3

SERVICE MANUAL- 1975 SCORPION BRUT
l 340MODEL
c. Pull rotor from shaft using puller.
d. Take out pulleys head screws holding
magneto to crankcase. Remove
magneto.
FIG. 1-25
1-14
ROTOR
440MODEL
c. Pull rotor from shaft using puller.
FIG. 1-24
d. Take out Phillips head screws holding
magneto to crankcase. Remove
magneto .
..
FIG. 1-26
j
)

)
I
(
340MODEL
e. Remove Phillips head screws holding
seal to crankc a se- Remove seal.
FIG. 1-27
SERVICE MANUAL· 1975 SCORPION BRUT
440MODEL
e. Remove Phillips head screws holding
seal to crankcase. Remove seal.
FIG. 1-28
1- 15

SERVICE MANUAL- 1975 SCORPION BRUT
DISASSEMBLY OF CRANKCASE
1. Remove 8 mm bolts (18-440, 12-
340) and 2-1 0 mm bolts.
2. To loosen crankcase, hold bottom
half firmly and tap top half with
plastic mallet.
3. Lift top half of crankcase off.
4. Lift crankshaft out of lower half of
crankcase.
1-16
FIG. 1-29
FIG. 1-30
FIG. 1-31
FIG. 1·32

ENGINE ASSEMBLY
( Assemble Crankcase/Crankshaft.
(
(
1. lay lower half of crankcase on
work bench. Grease.
2. Place crankshaft in crankcase
with positioning ring in groove.
3.
• Install rotor key in crankshaft
carefully. (440 Model only).
• Grease labyrinth seal and oil
bearings.
Apply gasket sealer on lower half
of crankcase.
• Place upper half of crankcase
on lower half.
SERVICE MANUAL- 1975 SCORPION BRUT
LABYRINTH
SEAL
FIG. 1-34
FIG. 1-33
FIG. 1-35
1-17

SERVICE MANUAL· 1975 SCORPION BRUT
4. Install crankcase bolts and torque
(See Specifications: P. 1- 4).
5. Install cylinder bose gaskets.
l-18
)
FIG. 1-36 )
FIG. 1-37
I

SEAL PLATE INSTALLATION
\
1 1. Measure distance from seal mounting
)
}
/
plate surface on case to outer race of end
bearing on shaft. (Use depth micrometer).
2. Select and install correct end gasket
depending upon depth measurement as
follows:
Depth Measurement
.091 and over
.08 1 to .091
.080 and l ess
Gasket Thickness
.2 mm (.003")
.3 mm (.012")
.5 mm (.020")
3. Bolt seal plate in position.
4. Bend lock tabs to secure plate bolts.
FIG. 1-40
SERVICE MANUAL • 1975 SCORPION BRUT
SEAL
MOUNTING
SURFACE
FIG. 1-38
FIG. 1-39
FIG. 1-41
1- 19

SERVICE MANUAL- 1975 SCORPION BRUT
PISTON INSTALLATION
1. Place piston pin bearings in con -
necting rods.
• Position spacers at ends of bear-
ings.
• Lubricate bearing s.
See Fig. 1-1 8.
2.
Install one {1) snap ring in each
piston before placing pistons on
rods.
3. Slip pistons over connecting rods
holding bear.ings and spacers in
position.
4. Insert pi s ton pin through pi s ton,
bearing and spacers.
elnstall remaining snap ring .
See Fig. 1- 16, and 1-17.
PISTON RING INSTALLATION
Expand ring until it just slips over
piston.
Do not expand any further than
neces s ary.
Pos ition rings so that ring notch slid es
over ring locating pin .
See Fig. 1- 42.
1- 20
FIG. 1-42