Mercury 1976 340 S/T, 1976 440 S/T Service Bulletin

Number: 76-9

CIRCULATE

TO:

GASOLINE/OIL RECOMMENDATIONS -

ALL MERCURY SNOWMOBILES

(Atwch

IMPORTANT: Supersedes all information previously published
line/oil recommendations: Service Manual, Operation and Maintenance
Manuals, Snowmobile Service Bulletins and "Fuel Warning Tags- Posters".

Recommended Oil(s)

Quicksilver Snowmobile
Quicksilver Formula 25 50:1

Quicksilver Formula
Quicksilver Formula 50 50:1

BIA!TC-W Rated

Bulletin Reference Sticker to

Fan Cooled and Free-Air Models

Ratio (1)

50:1

500

50:1

40:1

SNOWMOBILES

SERVICE MGR. PARTS MGR.

Page

1-6

of

Your Snowmobile Service Manual.)

Fan

Cooled

Gasoline (2) Ratio Gasoline (3)

Regular
Leaded

Motor

86

Octane)

Minimum

Average Octane

(80

20:1
20:1

20:1
20:1
20:1

Date :

MECHANICS

on

gaso-

Free-Air

100/130
AvGas

12/1/75

Place in Your

"Service Bulletins

Binder

(1) Ratio

(2)

(3)

of

25:1

is required

for

"Severe Service" operation. Refer
Service" definition.
For

1975

Model440
ignition
For
BTDC.
BTDC.

timing

Racing,

For

is retarded

use

100/130 AvGas and retard ignition

Trail Ride,

for

the

TIT

(Below CHASSIS Serial No. 4210250),

from

use

PREMIUM

first

.095"

(one)

tank-full

to

;,/Operation and Maintenance

BTDC

and retard

to

during engine

.080"

BTDC.

ignition

timing

timing

"Break-In"

use

from

.100"

from

PREMIUM, UNLESS

.100"

Liquid Cooled Models

Recommended Oil(s)

Quicksilver Formula
Quicksilver Snowmobile Oil

Quicksilver Formula

BIA!TC-W Rated 16:1

50

500

IMPORTANT: Some 1976 S/T "Operation and Maintenance Manuals
(C-90-74530)" recommended Quicksilver Snowmobile Oil, Quicksilver Formula
500

and BIA!fC-W Oils (all prediluted)

at

oils, ONLY,

a 16:1 ratio are permissible. CHANGE any

at a 20:1

the above recommendation (16: 1 ratio).

Liquid Cooled
Ratio Gasoline
20:1
16:1
16:1

ratio. Use

100/130 AvGas

of

these prediluted

of

these Manuals

period

Manual"

BTDC

BTDC

to

for

to

to

and/or

;,/Severe

.080"
.060"

~I:KYI~~

BULLETIN

TIIEI#'L

~~P.J

6 .....

n

~-=·

oe

wt"•"d""'

-KO

SNOWMOBILES

CIRCULATE

TO:

ZIN'Y

SERVICE MGR. PARTS MGR.

Date :

MECHANICS

r:

/tS-Tz-

12/15n5

Place

in

"Service Bulletin!

Your

Binder

A. Balancer Installation- 1976 Model340
B.

Driv

e Clutch Weights-

C.

Driv

e Outch Weights-

D. Lower

A.

BALANCER

(Attach Bulletin Reference Sticker

INSTALLATION

For
For

Cowl

ALL

ONLY

and Snow Flap Fasteners· All1976 Model250-340-440 Sno-Twisters

- 1976 Model

on

Section

1976 Model

1976

340

Model440

IMPORTANT: ALL 1976 Model250

ALL 1976 Mercury Sno-Twister Snowmobiles

[ 3.96mm] thick by

5.250"

[l3.34cm]

AU

1976 Model340

AU

1976 Model440

2C

In.dcx

S(f

S(f

SIT

diameter) between the rewind starter cup and lower pulley.

Strand

340

S(f

Page

(CHASSIS Serial No. 4495560

(CHASSIS Serial No. 4349537

440

Str

Snowmobiles
Str
Str

and 440 S/T Snowmobiles

of

Your Snowmobile Service Manual.)

and

and

Above)

already are equipped with the balancer.

MUST

BE equipped with a balancer (steel disc

Below)

The balancer (D-75961) stabilizes the crankshaft and prevents excessive vibration of the drive
clutch, thereby improving the life

IMMEDIATELY notify owners

MUST

BE INSTALLED (installation instructions following).

of

drive clutch components.

of

the above specifi

ed

Sno-Twister Snowmobiles

that

this balancer

IMPORTANT: A simple visual inspection via the water pump belt channel in the bell housing
can verify whether-or-not the balancer has been installed.

.156"

Order the required quantity of balancers and 4 screws for each balancer from your parts
distribution source. Credit for the balancers. screws and 0.3 hrs. labor per snowmobile
upon receipt

Nos

.) may be used to cover service

INSTALLATION

l.

Remove rewind starter assembly.

2. Remove 4 screws which secure rewind starter cup and low

of

a completed warranty claim. One warranty claim (listing individual CHASSIS Serial

to

all snowmobiles.

C-75961

C-10-75967

INSTRUCTIONS

Balancer

Scre

(1

per Snowmobile}

ws

(4 per Balancer)

er

pulley

to

rotor. RETAIN the 4

will be issued

lockwashcrs from the screws and discard the screws.

3.

Inslall balancer between lower pulley and s
IMPORTANT: Failure

to

damage

the rotor and could alter ignition timing.

a. Place MACHINED side of balanc

to

use the 4 lockwashers

er

b. Install lockwashers (retained in Step 2) on 4

(C-92-32609)

to

threads

of

screws and reinstall starter rewind cup with screws.

tart

er rewind cup.

on

the 4

NEW

retaining screws

against lower pulley (toward engine).

NEW

screws, apply Loctite Type

will

result in

"A"

4. Reinstall rewind starter assembly.

(OVER)

B.

DRIVE

CLUTCH WEIGHTS-

ALL1976

Model340 SIT

(Attach Bulletin Reference Sticker on Section

ALL 1976 Model

340

Sff

Snowmobiles

drive clutch assembly (6 weights per clutch). Some 340

4495867 and Below) were shipped from the factory with
these ARE NOT LEGAL for "Stock
1976

Model 340

INSPECTION PROCEDURE
l.

Part No. stamped into perimeter

INCORRECT:
CORRECT : XXXX-988- or XXXX-989-

2. OR, visual inspection

Str

Snowmobiles to check the drive clutch for correct

XXXX

088

088 088

of

the Part No. on the weights thru vent holes in drive clutch cover,

2C

Index Page

MUST

of

Your Snowmobile Service Manual.)

BE equipped with

SIT Snowmobiles (CHASSIS Serial No.

#106

II"

class racing.

of

drive clutch cover, as follows:

To

remedy, IMMEDIATELY notify owners

#135

weights (D-71737) in the

weights in the drive clutch, and

#135

weights.

follows:

INCORRECT:
CORRECT :

IMPORTANT:

XXXX

XXXX

If

106 (Color- Red)

135 (Color- Black)

the weights are incorrect and must be replaced, REMOVE the drive clutch
assembly from the engine before attempting clutch disassembly. Removal and/or installation
the drive

clutch~

works best

-·

with the aid

of

an arbor press.

of

as

of

Credit for the weights and 0.5 hrs. labor per snowmobile

will be issued upon receipt of a completed

warranty claim. One claim (listing individual CHASSIS Serial Nos.) may be used to cover service

all snowmobiles.

D-71737 Weight-

C.

DRIVE

(Attach Bulletin Reference Sticker on Section

ALL 1976 Model

CLUTCH WEIGHTS-

440

Sff

ALL1976

2C

Snowmobiles

Model440

MUST
drive clutch assembly (6 weights per clutch). Some
4349543 and Below) were shipped from

ill"

these ARE NOT LEGAL for "Stock
1976 Model440 SIT Snowmobiles

INSPECTION PROCEDURE
l.

Part No. stamped into perimeter of drive clutch cover, as follows:

INCORRECT:

CORRECT :

2. OR, visual inspection

XXXX
XXXX

089

-989-

089

of

the Part No. on the weights thru vent holes in drive clutch cover,

class racing.

to

check the drive clutch for correct # 106 weights.

Index

#135

SIT

Page

of

BE equipped with

440

the

factory with

To

(6 per Clutch Required)

Your Snowmobile Service Manual.)

#106

weights (D-71717) in the

SIT Snowmobiles (CHASSIS Serial No.

#123

remedy, IMMEDIATELY notify owners

weights in the drive clutch, and

follows:

INCORRECT:

XXXX

123

(Color-

Yellow)

to

of

as

CORRECT :

IMPORTANT:

XXXX

If

106

(Color-

the

weights are incorrect and must be replaced, REMOVE the drive clutch

Red)

assembly from the engine before attempting clutch disassembly. Removal and/or installation
the drive clutch cover works best --with the aid

of

an arbor press.

of

Credit for the weights and 0.5 hrs. labor per snowmobile will be issued upon receipt
warranty claim. One claim (listing individual CHASSIS Serial

~os.)

may

be

used

to

all snowmobiles.

of

a completed

cover service

to

D. LOWER COWL

Snowmobiles

(4ttach Bulletin Reference Sticker

LOWER COWL

To be sure
that

th<>

6 aluminum rivets, which secure the cowl

and

that

the lowf'r cowl remains securely fastened

D-71717 Weight-

SNOW FLAP

FASTENERS-

on

Section

2F

Index

#106

Page

ALL

of

to

diameter head - 3 located inside lower cowl in a line on each side

STEEL rivets (Mercury Part

X 5

/8"

shank

SNOW FLAP

[15.9mm) diameter head with

. C-17-76047)

or

an equivalent steel riv

3/8"

r9.5mm) toY:!" [12.7mm] grip range).

No

Check the rivets which secure the snow flap and mounting

out

from pulling
has a
(13/64"

If
or

"backing"

[5.16mm] J.D. x

the

rivets arc

equivalent) with the backing washers.

thru the snow flap, make sure

washer on

not

equipped with these backing washers, remove and install new rivets (C-17-64817

<>ach

Y2"

[l2.7mm]

riv

et

(Mercury Part No. C-12-21273) or an equivalent washer
O.D. x

that

l/16"

the

(6 per Clutch Required)

1976 Model 250-340-440 Sno-Twister

Your Snowmobile Service Manual.)

to

the front crossmember,

the

front

crossmember (silver colored,
of

crossmember), be replaced with

et

str

ip

to the chassis.

"clinch"

[l.59mm]

end

thick).

of

(3/16"

the rivet (inside

we

[4.8mm]

To

prevent

recommend

the

5/8"

diameter

the

rivet

tunnel)

0

0

0

.J'

~I:KY

B

ULLETIN

l\;1:

MERCURY SNOWMOBILES with ARCTIC DRIVE CLUTCH

Internal Drive Clutch Component Information

TIIEH

~!!",&

I

~

701.11

Ul\lf•I'IC•

of

<WI$l.nd1t19

.......

CIRCULATE

TO:

SNOWMOBILES

SERVICE MGR.

PARTS MGR. MECHANICS

Number: 76-13

Date : 12/22/75

Place

in

"Service Bulletins

Your

Binder

"Stock"

MODEL

CHASSIS Serial No.

MERCURY PART
LAST

3 DIGITS

OUTSIDE

DRIVE

DRIVE CLUTCH WEIGHTS

DRIVE CLUTCH RAMPS

of

CLUTCH SPRING
Color
No.

of

Turns 3.9 3.9 3.9

Mercury Part No.

Color

No. Stamped on Weights

Gram Weight
Outside Diameter
Mercury Part No.

No. Stamped on Ramps
Drawing
Mercury Part No.

of

NAME

NO

. D-52-71571 D-52-71572 D-52-74255 D-52-74256 D-52-75098 D-52-75099 D-52·75100

of

NO. STAMPED ON

DRIVE

CLUTCH COVER

Ramp Profile

Drive

4207500 4206250 4347125 4347124 4495560 4495559 4349324

061

Blue Blue Blue Blue

C-24-71517

Red
0146·106 0146·105 0146-106 0146-286 0146·106 0146·135CD

5.958g 7.858g 5.958g 8.800g 5.958g

0.530" 0.598"
D-71717

None

Figure 1
D-71496

Clutch

1975 1975 1976 1976 1976

340

srr

Below Below Below Above Below Above

440S

062 077 080

C-24-71517 C-24·71517 C-24-71517 C-24-74992 C-

Black

D-71716 D-71717 D-74125 D-71717 D-71737

None 292 293

0

Figure 1 0

(!)

D-71496 (! D-74123 D-74124 D-75908 D-75177

Component

/T 340 TIT

Red

0.530"

Figure 3 Figure 4

440 TIT

3.9

Yellow

0.629"

Chart

1976 1976

25o

srr

081

Green

5.0 5.0

Red

0.530" 0.471"

None
Figure 5 Figure 6

340S!T

088

Green

24-74992 C-24-74992

Black

4.479g

None

CD

CD

440

srr

Above

089

Green

5.0

Red
0146-106

5.958g

0.530"
D-71717

None
Figure 6
D-75177

CD

Optional Clutch Ramps (D-74857A

Q)

A few 1976 Model
drive clutch weights. Weights stamped 0146-135 (D-71137)
clutches.

: :

..

-

ACTUAL

Figure 1. D-71496 Drive Clutch
Ramp Profile (1975

440

S/T)

SIZE

340

S/T

340

&

1,

Figure

SIT

snowmobiles were shipped from the factory

2)

are available

for

trail riding.

MUST

'

·'

ACTUAL

Figure
Clutch Ramp Profile (Trail Ramp
for

2. D-74857A1 Drive

1975

340

(OVER)

S/T

& 440 S/T)

SIZE

with

INCORRECT

BE

INSTALLED

/

in

these

/

/

l J

ACTUAL

Figure 3. D-74123 Drive Clutch

Ramp Profile (1976

SIZE

340

T/T)

ACTUAL SIZE

Figure
Ramp

4.

D-74124 Drive Clutch

Profile (1976 440 TIT)

ACTUAL SIZE

Figure 5. D-75908 Drive
Ramp

Profile (1976 250 SIT)

Cluttch

ACTUAL

Figure
Ramp
440 SIT)

6.

D-75177 Drive Clutch

Profile (1976 340 SIT &

SIZE

MODEL

Drive Clutch Elevation
Drive Clutch Modification
Drive Clutch Trail Ride

N.A. -

Full

Throttle

Engine
Increase

Engine

Decrease
Engine

Q)

Six

Not

RPM

RPM

RPM

NAME

Available

Gram Weight

light

Heavy

of

these

Kit

Kit

3.058g 0146-108

3.725g 0146-175

4.479g

4.958g 0146-107

5.958g 0146-106

6.992g

7.858g

8.800g 0146-286

weights are included

Drive

1975 1975 1976 1976

340

SIT

D-71712A1

Kit

D-71711A 1 U-71711A 1
D-74857 A 1

D-71712A 1

D-74857A 1 N.A. N.A.

Drive

No. Stamped Outside Diameter

on Weight

CD0
CD0CD

0146-135

CD0CDCDCD
CD

CD

CD

CDCD

0146-123
0146-105

CD0CD
CD
0

in

Clutch

440S/T

D-74124A 1

Clutch

Drive Clutch

Accessories

1976

250

340

TIT

N.A. N.A. D-71711A2

Weight

Color

Modificat~on

D-i11716A 1

of

Weight

Yellow

Red

Black

White

Red

Yellow

Black

Yellow

440

TIT

Chart

I

Kit

of

0.406"

0.437"

0.471"

0.491"

0.530"

0.568"

0.598"

0.629"

(D-71711 A 1

SIT

D-71712A2

N.A. N.A.

Weight

1976 1976

340

S/T
D-71712A2 D-71712A2
D-71711

D-71731
D-71735
D-71737
D-71736 Q)

D-71717
D-71734
D-71716
D-74125

CD
CD 0 CD
CD

CDCD

CD0CD

CD

0

).

A2

D-71711A2

Part No.

0
0 Q)

CD CD

440SIT

N.A.

CD CD

@ Six

G)

Six

Q)

Six

(D Six

CD

Six

of
of

of
of
of

these

weights are included

these

weights

these

weights

these

weights are included

these

weights

are
are

are

included
included

included

in

Drive Clutch

in

Drive Clutch Elevation ,Kit (D-71712A

in

Drive Clutch Elevation

in

Drive Clutch Elevation

in

Drive Clutch Elevation

Modificat~on

Kit

(D-71711 A2).

Kit

(D-71712A2).

Kit

(D-71716A 1

Kit

(D-74124A

1).

).

1).

5NU•TWISTER

TIPSTER

HI-PERFORMANCE

(Flash 'Inside'

INTRODUCTION

It's

official!
season
sponsor
quick
months,
local drivers

The Sno-Twisters leaped
the final around the oval, all on Saturday. Then Sunday the crew came

honors

So, here's the bonus! We,

make the run
Sno-Twisters at Brandt's Lodge:

ENGINE

After

months

- on good old Alaskan snow ­of

the

kick-off

in

geography,

that

can

who

in

cross-country.

you'll

be real mean blizzard

had

"WIN"

for

the

Their Sno-Twister Customers)

of

spinning on hay

race meeting on

find

it

160 miles northeast

written

to

the

of

course, are happy

roses.

front

The

all over

following

Info

for

Mercury Snowmobile Dealers

and

straw,

has

opened

Nov

. .3rd and

territory.

their

and stayed there

with

4th

Ignoring all impending hazards, however, were

Sno-Twisters.

to

share

procedures were

11/16n3

or

a resounding

was Brandt's Lodge

of

Anchorage. Give or take a couple

to

win

the secrets

on

just

plain

grass,

"Margin

all three heats in

right

back

of

success

used

in setting-up the champion

NO.

to

Z-i-p

the snowmobile

for

Mercury".

...

and,

if

their

400

to

grab

so

that

you,

74-1

to

Eager

you're

class,
first

too,

real

of

plus

place

can

1. Check

2.

Adjust

engagement and

3. Check
The

spot-on
full
chocolate brown

timing

idle slow enough

for

following

for

racing. A Champion N55G plug

throttle

proper jetting.

jet

speed

BELOW 2000'

Temperature

Above

0.

Below

If

your

Mercury dealer doesn't
fails, a
340 jet.

Move
fourth

#53

drill

jet

needle

(4) notch

@3000 RPM

belt

sizes

run, the correct

color-

300

3QO

oo

(.059 dia.) corresponds

to

richer position

from

the

.100"

.±.

to

allow

drag, resulting in a slower start

will

serve

as

a guide, however, a proper plug check

must never appear whitish/grey.)

ELEVATION

Jet Size

290

to

320

to
to

330

have

jets,

by

top

of

the

jet

.005"

BTDC.

clutch

fuel/air

300
330
360

one notch; i.e. the retaining
needle.

to

reset. (Too high idle

off

is

easier

to

read

mixture

try

any dealer stocking

to a 320

will

jet, and a

the line.)

and

is

cause

2000'

Subtract 1 0

1/16

speed

suitable

plug electrode

to

Mikuni

drill

for

4000'

ELEVATION

from

the

carburetor parts.

(.0625 dia.) corresponds

clip

should be moved

is

the

racing.

jet

will

only

to

sizes

cause

(After

partial

way

to

100 yd.

have a light

I isted on left.

If

all

else

to

to

get

a

the

DRIVE

SHEAVE

1. Inspect clutch and lube per instructions in the Owners "Operation

(C-90.68019).

2. Check engagement
Use

an

3.

accurate tachometer

RPM

and adjust

to

check engagement

if

necessary.

(OVER)

speed.

(USSA

says

and

Maintenance

4000

RPM

Manual"

max.)

DRIVEN

SHEAVE

1. Check alignment per the manual.

2. Set spring preload

3. US!: A NEW

4.

Adjust

belt tension per the manual.

at 2 full

BELT.

cams.

FUEL

ICE STUDS and

SLIDER/TRACK

OIL

Use

a 20:1 fuel-oil

Mercury Formula 25 Mercury Formula

NOTE:

Carbide wear
and

an

Ice studs (D-68441) must be installed on the track. A good starting
on each side,
in the center band
washers

You

may prefer

effort

considerably.

You

CARBIDES

skegs

oversize washer

utilizing

to

space

ADJUSTMENT

mix.

Only

the

following

Castrol Synthetic High Performance Snowmobile Oil

may

want

to

clamp

(D-68440) must

used

above the ski

the holes in the track bars. One

of

the track

the studs

to

set the steering in the

See

up

your

to

"Operation

or

wire the fuel lines

be

installed

but

should be attached

the

3/8"

oils are known

at

for

racing. The ski holes may need

to

make the carbide

or

two

to

allowable.

low

effort

and

position, since the carbides increase the steering

Maintenance Manual".

to

be

satisfactory

50

the fuel pump.

fit

properly.

point

additional rows

the rubber

for

SNO-TWISTER:

Mercury Formula

to

be

is

to

install eleven studs

of

only,

eleven

not

thru

can

the bar.

500

drilled

be added

out

Use

The track must be adjusted
run smoother

is

load
track.

As outlined
that
position. Set yours

TETHER

Disconnect

engine.

Attach

must be pulled free before the tether is disconnected.

Check the tether switch operation. Moisture

malfunction. Gasoline de-icer

COWL

The aluminum hinge rivets should be replaced
should be removed

taken

for

SWITCH

a paper

best

if

the drive sprockets

out

through the wear plates inside the tunnel,

in

your

Owners Manual, handling (oversteer and understeer)

weight

on-off

transfer, the rear springs should be

up

and test

switch wire

clip

to

or

taped

for

proper tension

are

lubricated

prior

to

racing.

from

#3

stud

the tether switch cord

will

eliminate the moisture.

and

the screws secured

as

outlined in

with

of

terminal block,

and

hook

the

will

cause

with

large

with

your

Owners Manual. The track

grease

the points

silicone sealer.

so

set

clip

head

soft

(STP

be

sure

and the

to

prevent accidentally stopping the

on the

to

steel rivets

works well). Most

to

lubricate the

can

be

adjusted.

front

throttle

freeze, resulting in a switch

cable

or

bolts. The headlight

edge

springs

so

that

of

the side

We

in

the clip

of

found

the %

will

the

**IMPORTANT

NOTE:

U.S.S.A.
we cannot

has

ruled

that

use

the boggie wheel

kits

for

racing.

S

no-

Twister I

Hi-Performance

Tipster

No. 75-1 (6/1174)

Mercury Marine
"Sno-Twister

To

get
included
manufactured

MR. DEALER - Mercury Marine has

Registration Cards. We've

We've
snowmobiles
information

/ Hi-Performance

the

project

in

the

after

done

is

introducing

in

gear, the

"Snowmobile

Sept.

1,

1974.

another

Tipster",

following

Information"

FREE

aimed

"IMPORTANT"

IMPORTANT

added

this

in response

for

racing)

in "Sno-Twister/Hi.Performance

who

RACING0to

to

many

wish

to

receive,

Important

Sno-Twister/Hi-Performance

customer

primarily

envelope

made

requests

from
Tipster"

for

an

the

the

Info

about

benefit:

racing machines.

shipped

important

"Primary

from

factory,

bulletins

Owner

Tipster

with

change

Use" section

owners

owner

on

Snowmobile

mailing list directive will

racing.

Registration

Tipster

direct

all Mercury

(primarily use

to

direct

mailing

Snowmobile

of

the

mail

of

and

Mailing List

of

the

new

be

Snowmobiles

card.

their

latest

To

compile

that

1)

intended

the

factory.

We're sure

service.

Only

you

We'll

also

advise
should
the

This

time-saving tips.

be

properly

customer

"Tipster"

will

such a customer

you

fill

out

and

mark

that

every racing

can

get him

owners

checked

be

mailed

sheet

will

mailing list via

all registration cards, 2)

the

registration

on

the

in

their

"Operation

on

the

the

"Tipster"

be

used exclusively

owner

racing

new

card

accordingly

will

"Tipster"

and

machine's

bulletin.

to

direct

you

ascertain

want

to

take

list! If

Maintenance"

Registration Card

notify

owners

computer

from

and

3)

you

advantage

he

races,

manual

of

mailing,
the

promptly

of

check

high

performance

it

is ESSENTIAL

owner

this

that,
under

the
mail all cards

FREE.

RACINGD.

C-90-71050 (5174)

if racing

RACING 0

primary

direct

information

use

to

mail

is

intended,

so

it

that

and

IMPORTANT:

identical

an

mailing

The

service is

at

the

same

intended

time.

strictly

as

an

owner

benefit.

Dealers still will receive

Sno-

Twister I

Hi-Performance

Tipster

POSSESSION

Possession

the

driver ample time

competition.

of

INITIAL SETUP

After receiving a Sno-Twister,
even disassemble
components and

precision

that

• Pay special attention
secure trigger and

NOTICE:
order,
75-3
advise
Lac,

Sno-Twister/Hi-Performance

starting

with

you

desire

Marine

and

give

75-1.

previous
Publications

the

•·

and

Mercury

WI

54935.

1975 SNO-TWISTER- (340

a Sno-Twister well

to

it

completely

their

assemblies meet with your satisfaction.

a surgeon would use.

stator

in

advance

get acquainted with

you

may

to

familiarize yourself with

It

to

all

nut

to

crankcase.

If

the

first

first

copy

"Tipster"

Dept., P .0.

number

S(T-

of

want

"Tipsters"

that

the

the

to

are in numerical

you

receive is

issues (75-1

Box

you

received.

440

S(T)-

'74-'75 racing season can be a very big assist.

sled and

thoroughly check

brings results!

and

bolt torque specifications.

(example)

and

75-2) -

1108,

Fond

du

No. 75-2

(11

120174)

COMPETITION SETUP INFORMATION

to

properly break it

the

engine assembly and possibly

all

the

parts and

If

so, rebuild

Use

the

"loctite"

in

before entering

to

make certain

engine with

on

the

all bolts

It

gives

that

all

care and

that

• When assembling cylinders
no

with

gasket overhang. Make certain

to

cylinder.

• Check carburetor float levels and adjust high and low speed mixture screws

• Reinstall engine assembly, then check

tension, track tension and alignment and adjust

BREAK -IN PERIOD

IMPORTANT: During break-in period, a slightly rich high speed mixture adjustment

Use

a good premium gasoline and Mere Snowmobile

the

mixture for

for

short

durations only --avoid sustained full

throttle

setting. Check spark plugs often

first few hours

Become familiar with

characteristics. This

is

the

very important

feel

of

of

RACE PREPARATION (BASIC)

Cleaning and Inspection: After

the

Visually check

engine and chassis for worn
head gaskets, pistons, rings and cylinders for excess wear, cracks, chipped chrome, etc. Repair
components as necessary. Check piston

the

crankcase, make sure

that

the

torque

to

running (until piston rings have seated properly). Run

throttle

to

ensure

the

sled (clutch engagement, shifting, sound, etc) and its handling

for

later testing.

that

break-in period

or

that

the

transfer ports are lined

cylinder head

converter alignment, drive

specifications (refer

Oil

when mixing gas/oil. Make

dome

is

centered directly over

to

specifications.

belt

tension, drive chain

to

Owner's Manual).

operation and prolonged operation
engine

is

is

not

overheated.

completed, thoroughly clean the snowmobile.

up

is

advisable.

it

a slightly richer

at

high

at a constant

broken parts. Remove cylinder heads and inspect

or

fit

and ring clearances (end gap and side clearance).

correctly,

the

RPM

replace

Secure exhaust headers

to

cylinders, using safety wire

Check ignition timing (should

be

.100"

BTDC [21%0]

or

).

bearing

mount

type

"Loctite"

on

hex screws.

Check ski alignment (parallel, measuring
rod attaching hole closest

to

the

steering shaft.

front

and rear

Try

both

of

skis).

For

positions for

easier (slower) steering, use

your

preference.

the

tie

Check track and suspension: Track tension
lubrication), shock absorbers (dampening/leakage), idler wheels (wear and free bearing movement), slide
wear bars

parts as necessary.

Chaincase: Clean

Check brake assembly (cam, pin and pucks for wear)

and

chassis

and

rub

strips. Check all

inspect chain, sprockets, jackshaft and bearings.

RACE PREPARATION (FINAL)

Check electrical wiring: Disconnect emergency
terminal block (located behind dash). Be sure
secure and in good condition. Red wire from electronic pack
connects

Install a "race-proven" ignition safety
carburetion; re-check
Manual)
slides and adjust idle speed, making sure full
freely. Check all fuel lines
crimped.

to

to

coil

on

rewind side. Make certain

carburetor

suit

conditions (temperature

and

hoses.

and

alignment, suspension cross shafts (wear/bending -

nuts

and bolts for wear

"free

floating" and correctly adjusted.

stop

switch (red switch

that

ground wire from

that

CD

wiring connectors are coupled securely.

stop

switch (tether switch)

float levels. Adjust high speed mixture needles (as outlined

and

Be

positive

elevation)

throttle

that

that

operation

the

lines are secure

connects

will

and

proper

to

be

encountered. Synchronize

is

attained and

torque.

on

throttle

CD

mounting base

to

PTO side coil; white wire

suit rider. Check

on

fittings and

Repair

throttle

control)

not

or

replace

from

to

engine is

and

adjust

in

Owner's

throttle

cable moves

pinched

or

Check
system is mounted securely.

Drive sheave (clutch): disassemble
wear
are properly seated in movable face. Engagement
lowered
be sure
bind fiber

Driven sheave: Disassemble and clean. Check condition
necessary. Reassemble
required (approximately 2 ramps)
(8250

Torque converter alignment: Check
Inspect drive belt

about

Drive chain: Drain and refill chaincase
Check

exhaust

and/or

by

to

RPM)

condition

and

system: Inspect

binding. Check all moving

removing them. No

match alignment mark

bushing-

- refer

adjust chain tension

no

lubrication is necessary.

and

to

Owner's Manual.

for

wear, distortion,

of

belt,

replace

for

more

lightly lubricate shaft and wear plates. Adjust return spring preload as

it-

to

cracks, broken parts

and

clean. Check fiber bushings

parts

for wear and restricted movement. Make sure

RPM

than

four

(4) spacers are allowed. When reassembling drive sheave,

on

movable sheave with mark

to

attain maximum recommended

and

adjust alignment (parallel

burn

spots

and

cracking. Check drive

refer

to

Owner's Manual.

with

3 oz. (3.1 imp. oz.)

specifications.

and

missing coupler springs. Make certain

in

movable and fixed sheaves for

can

be

of

raised

on

torque

of

by

adding spacers

sheave cover

bracket wear plates. Replace if

RPM

and

offset

automatic transmission fluid (ATF).

and

take

at

wide open

distance between sheaves).

belt

tension. If

that

on

care

that

ramps

spring

not

throttle

in

doubt

or

to

Suspension adjustments: Understeer and oversteer can be varied
cross shaft. Rear shocks can

weight transfer requires a

soft

be

adjusted for firm

settin9

at

rear-

refer

or

soft

ride, depending upon rider preference. Best

to

Owner's Manual.

by

changing spring tension on

front

Track/slide suspension alignment: Align track

first

to

slides, then

to

chassis

tunnel.

NOTE: Because the front control arm always is

suspension mounting holes slightly

achieve

Traction devices: Three types
surfaces

Placement and pattern

rivet in the outside

Track lubrication: Lubrication
of

tunnel and between drive sprockets

Skis/carbide wear
Marine.

perfect alignment

and

conditions.

ends

skegs:

of

D-68441
D-71925

D-71926

are

strictly rider preference, depending upon rider style and racing surface. The

of

each

Carbide wear

D-68440-1
D-71334

the

of

track bar

of

and

slider

suspension

studs

are

can

the track

and

skegs

track.

in

compression,

it

may

be

necessary to rework the

adjust alignment with the suspension bolts loose in order to

inside

available

Mere Stud (22
Mere Scat Stud (22
Mere

be

removed,

can

be

beneficiial

(STP

are

a MUST

Carbide
Carbide

the

chassis

from

Mercury Marine

Pes.

Carbi•tle

lubri•cant works well.)

Stud (22

if

absolutely

by

for

stock racing and

Sk•eg

{Pair-

Sk•eg

(Pair -

tunnel.

Per

Package)

Pes.

Per

Pes.

necessary,

reducing drag between track

10"

Carbide Inserts)

6"

Carbide Inserts)

for

various types

Package)

Per

Package)

to

are

available

of

place a stud.

and

from

Mercury

racing

sides

or

Badly chipped, bent
carbide

Special application:

application; i.e., high elevation,

skegs

influence handling

Driver Sprockets {340

broken carbide

At

this

time, the following equipment

D-1393-5872A 1
D-1393-5854A 1
D-71712A1
D-71711A1

C-58601A1

(1) D-69757-12

D-68439
D-64684 14
D-63318A 1

D-64131

(1)

One C-23-69842 spacer

skegs

should

to

a high degree and, again,

cross

country

SIT

and 440 SIT)

12

Tooth

13 Tooth

Tooth

15

Tooth

16 Tooth

must

be

racing and modified racing:

High
High
High
Modified Drive
Bogie

used with 12

be

replaced immediately. Placement

are

mostly rider preference.

is

available

Eleva1tion
Eleva1tion
Eleva1

tion Drive

WheEl!

prive

(2)1

D-71483

(2)1

Kit -340

78

Carburetor
Carburetor

Sheave

Chain {340

pitch chain

from

Kit
Kit • 440

Sheave

Kit-

SIT and

Mercury Marine

- 340

Kit

- 340

340

SIT and

440

SIT

and

must

be

sprocket.

tooth

sprocket.

and

length

for

S/T
SIT

SIT

and

440

440

SIT

SIT

440

S/T)

78 pitch length

used with

16

of

special

S/T

tooth

CONCLUSION

The aforementioned steps
Sno-Twister
will--

produce a competitive Sno-Twister

for

competition. Hard

have

touched basically on major

work,

patience, thorouuhness

that

will

win

aspects

consistently.

of

setting

and

a strong desire

up

a 1975 Mercury

to

win can--

and

-

MERCURY MARINE - CERTIFIED SNOWMOBILE SPECIFICATIONS

M

ODEL

NAME

IN

E SPECIFICAT IONS

ENG

Engine Manufacturer
Engine

Model

No.

of

Cylinders

Engine Displacement

of

Cooling

Type
Bore 65.0
Stroke
Ignition
Min.

Compressed Head
Gasket Thickness
Min.

Compressed

Gasket Thickness

~~olume

<D

of

Spark Plug Hole
Crankcase Volume
Overall Length
Depth

-Top

to

Bottom

Depth·

Top

to

Top

of

Depth-

Top

to

Top

of

No.

of

Transfer Ports 4

Width

of
of

Width

Width

of

Height

of

Height

of

Weight-Piston Assembly
Complete

Overall Height
No.

of

Rings per Piston 1

Ring Type
Ring Thickness

Crankcase
of

Crar>kshaft

Main Bearing
Muffler

Make

DBA

Level 82+2

Head Pipe Length

Piston @

Base

Head

to

Top

of

Cylinder 109.0+0.01

of

Cylinder

of

Intake Port

of

Cylinder

Exhaust

Port

of

Cylinder

Transfer

Transfer Ports

Intake Ports 46.0
Exhaust Ports 40.0
Transfer Ports

Intake Ports 29.0

Face

Type

of

to

Port

Piston

Center

TDC

SNO-TWISTER

Kohler
K400-2RS
2

398.2
FA

60.0
CD

0.95

0.35

of

19.0

290.0

90.5

30.0

47.0

32.0/11.7

13.0

300gr.:!:,20gr

71.7

L-Ring

2.0

70.0

Sea

led-Ball

Mere/Donaldson

98.5

1974

NOTE:
Inches

Kohler Kohler Kohler Kohler
K340-2RS K440-2RS
2

339.3 429.4 435.8 338.1 437.9
FA

60.0 67.5 68.0 62.0 66.0

60.0 60.0 60.0 56.0 64.0
CD CD CD

1.2

0.3

14.7

305.0

109.0±.5

90.Q±1.5 95.3±1.5 92.0+.75/-1.0

29.5_±1.5 29.0_±1.5

46.25±1.5
4

33.0.:!:,1.5/

45.0+1.5 43.0+1.5 48.0+1.0 37.0+1.0

37.0;!:1.5 43.0±1.5 42.4+.75 37.0+.75 40.0+1.0

14.0+1.0

28.5+1.0 30.3+1.0 24.0+.5 22.5+.5
240gr;!:10gr

67.5+.55
1 1 2 2
Dykes Keystone Dykes Keystone

2.0+.08 2.5+.08 2.0+.08 2.0+.08

70.0±.5 70.0;!:.5 70.0±.2 58.0;!:.1 70.23±.2

Sealed-Ball
Mercury
82+2

117.0+2 167.6+2

All

length

(");A

ll

Volume Is in C

1975 1975

340

S/T

12.5±1.0

Measurements Are in Milli

ubic

Centimete

440S/T

2 2 2 2

FA

0,7

0.3

19.0

305.0

109.0+.5

46.25.:!:,1.5
4 4 2 4

33.0+1.5/

13.0

;!:

1.0 13.7+1.0

14.0+1.0 13.7+1.0 14.0

310gr

;t

10gr 335gr;t10% 240gr;!:10%

70.7+.5~

Sealed-Ball Sealed-Ball
Mercury Mercury
82+2 82+2 82+2 82+2

1975

440

K440-2RS K340-2AX KEC-440/22

Fa

n

1.1

0.3

21

.7 17.7

630.0+10% 463.0+10% 931.0+10%

109.0 + .1/-.2 98.3+.2

33.5+.4/-.6 34.43+ .4/-.6

47 .8+ .6/·1.2 43.8+ .6/-1

35.0+1.0/

71.7+.5 64.1+.5 71.42+.5

"L"

& Rectangular

"Y"-Manifold

meters

, unless

Spec

rs (Conversion Table Below).

TIT

1975

340 S/R 440 M/X

Fan

Mag

1.2

0.3 0.3

84.3+.75/-1.0

.2

27.0.:!:,1.0

:!:_1.

0 13.5+1.0

"L"

& R,ectangular Rectangular

Sea

led-Ball

ACS

24.5"+.25"

ifi

Kioritz

Fan

Mag

1.1

21.4_±5%

115.95+.5
Reed

37.5_±1.0

51.5.:!:,1.0

85.0_±2.0

Reed Valve

Reed
307gr±10%

2

1.5+0.1

Sea
Cowl

15.25"+.25"

led-Ball

ed

1975

Valve

Valve

1975 1975

440 S/R

Kioritz
KEC-440/22
2

437.9 644
Fan

66.0

64.0 65.07

Mag

1.1

0.3

21.4:!_5%

931.0+10%

115.95+.5 174.62
Reed

Valve

37.5_±1.0

51.5.:!:,1.0
4 2

85.0.:!:,2.0
Reed

Valve

40.0+1.0

13.5+1.0

Reed

Valve Reed Valve

307gr:!:_10%

71.42+.5 75.41
2 3

Rectangular Cast Iron

1.5+0.1 1.57

70.23;!:.2

Sealed-Ball

Cowl Mercury

82+2 82+2

15.25";!:.25" 127.0

Markll

Mercury
Markll

2

Fan

79.37

CD
N.A.

N.A.

28.5
N.A.

Boost • 53.08

39.11

50.80

35.05
Reed Valve

47.0

20.32

491.68gr

1-Piece

Sealed-Ball

~

~

I

~

.....

9

~

::r

-·

C3l

~

.!.'%

.,..

...

1

i

~

3

:a

g:

n

..

...

~

'tl

0~

:

!l

-·

:;·

;;;

g

3

-·

~·

~

~

~

~.

~

~

~

Q

~

~

~

!;'t~a~

!'

-·

w

:;16:-"c;

~~g:Sl~

~;:;

o.;t,g>

t:~~.g

....

C~-t

::l

3: ~ ...

0.

91

~-

i'

a·

Cl)

-o-a

g.

c ; .

co!!:<:;;~

:.

c:r

o·

~

~.:;;

::l g

-4:!:

3

"'

-·

O'tl

i

~

i g

...

,..

""'"0

g.~

~<

..

~

~-<

.. 0

<.

'"e'"

Og'tn-.~

c

-lll

~

)( ~ !2.

4\):::.:...~CD

[ 0

..

00::~"'

•

.,

0.

0

'-J:

&_1,113~

1\.)'tl

o.-&f.l

C

I--

~

~

~

.

~

I

~

~

"""'

i\;

~

...........

~

.........::

~

~

(I)

CARBURETOR

Make/Model No.

per

Engine

No.
Venturi -Smallest

Diameter in
Throttle

Downstream
Choke

DRI

VE CLUTCH

Make/Model No. Comet/100C XXXX-061
Engagement Speed
No.

Spring Wire Diameter

No.
Arm/Roller

DRIVEN CLUTCH

Make/Model No.
Spring Wire Diameter

No.
Ramp Angle

CHASSIS/SUSPENSION

Chassis

Suspension
Chassis
Ski Length
Ski Width 117+3.1 117 .6+1.5 117 .6+1.5 117.6+1.5

TRACK

Make Goodyear Goodyear Goodyear Goodyear Goodyear Goodyear Goodyear Mercury
Material

Width
Length ­Track Drive Sprocket Teeth

CHA

lNCASE

Standard Drive Sprocket
No.

Standard Driven Sprocket
No.

Optional Drive Sprockets
No.

Optional Driven Sprockets
No. of Teeth

Snowmobile Weight(Pounds

Throat

Bore - Largest Dia.

of

Butterfly

of

Springs/Color

of

Coils 4.8

Weight 38.6gr+.5gr 18gr+1.5gr 22gr+1.5gr 50.08gr+ .5gr 40.12gr+.5gr

of

Coils

Model

Length

0 .D.

of

Teeth

of

Teeth

of

Teeth

MikuniNM·36 Mikuni/36/34RS
2

36.0 36.0 36.0

37.0 36.12
Yes Yes Yes

3800-4000
1/Red 1/Biue 1 /Blue

4.75

Comet/90D Salsbury/152110

4.75
6 6.25
45°

66769 70729 70729 72006 66602/70238 68345 69869 66011
Slide Rail

1880+6.3 2235+6
1000±6.3 952.5+3 952.5+3 952.5+3 1008.4+3 1008.4+3 1008.4+3 993.78

Rubber/ Rubber/ Rubber/ Rubber/

Steel Bars Steel Bars Steel Bars Steel Bars

381+3.2 381.0+3/ -1.5 381.0+3/-1.5

2820 2816.4+12.5 2816.4+12.5 2816.4+12.5

2 2

Arctic

Cat/

RPM

2)

4000RPM Max.

92"

.1

3.9 3.9

.192" .192"

41° 41°

Slide Rail

9 9

15
34 34 34 34

13-14-16 12-13-15-16-17 12-13-14-16-17

.A.

N
360+10 365

14

N.A. N

Mikuni/36/44RS

36.12 36.1

Arctic

Cat/

XXXX-062

2)4000

RPM

.192"

Salsbury/152110 Salsbury/850 Salsbury/850 Salsbury/850 Mercury Salsbury

6.25 6.25+.2

Slide Rail Slide Rail Slide Rail
2235+6

9

15 17 15

.A.

365 365 350 390 380 500

MikuniNM
2 1 1 1

36.0 39.7

Yes

Salsbury/850

Max. 3300 RPM+10% 3500 RPM+10% 3500 RPM+10% 3400 RPM+10%

1/Piain

4.32 4.32

5.4+.2 5.4+.2 5.4+.2

4.88 3.96 3.

350

2235+6

381.0+3/-1.5 387.35

9

12-13·14-15-16-18 12-13-14-16·17
28-36·38-40

·36 Walbro/WDA·50

41.3
Yes

Salsbury/850 Salsbury

1/Piain

5+.2 5+.2 6+.2

320

+6

2209.8

136.6+1.5 136.6+1.5 136.6+1.5

Rubber/Grouser Rubber

3072.4

8

36 36 28

28-34·38-40 28-34-38-40

Walbro/WDA-47 Walbro/WDA-47 Walbro/WRA-3

2

39.7

41.3
Yes Yes Yes

/850

1/Piain 1/Piain 1/Piain

4.32 4.74 4.3

43.86gr+.5gr 65.32gr+.5gr 51.32gr+.5gr

96

32°

Bogie Wheel Slide Rail Swing Frame
2247+6

387.35 387.35 431.8

3009.9

39.7

41.3 38.1

Mercury Salsbury/850

5.2+.2

5.71

40°

2247+6

Rubber/Grouser Rubber

3072.4 3327.4

32.5

3200 RPM+10%

5.4±.2

4.3
7+.2
32°

2521

152.4

8 8 8

17

12-13-14-15-16-18 12-13-14-15·16·17

-18

18

34-36·38·40 28-34·38·40

16
36

12·13·14-15·17 ·18

/850

NA. a Not

Applicable

METRIC CONVERSION: 1mm (millimeter) =

cc

(cubic centimeter) = 0.06 cu.in.; 1 1

1

0.0394"

(inch); 1 gr (gram) = 0.04 oz.;

b.

(pound) = 0.4536kg (kilogram)

(D

0-4 Spacers (.06 Thick)

to

Achieve 4000 RPM Max.

Sno-

Twister I

Hi-Performan

ce

Tipster

NOTICE: $no-Twister/Hi-Performance

order,

starting

with

75-3 ••

and

advise Mercury Marine Publications

lac,

WI

54935,

75-1.

you

desire previous

and

give

Driven

We

have received a few reports

in

crack (as shown

Figure

Thus far, complete breakage has
At

this time, and only

support

brace (as shown in Figure

as

that

1)

because

not

occurred.

a temporary measure,

2)

to

A new, stronger pillow block with a

If

the

the

first

Shaft

the

driven shaft pillow block (D-71007) has developed a small

of

the

reinforce
support

"Tipsters"

first

copy

"Tipster"

number

Dept.,

issues (75-1
P.O.

that

Pillow Block -

torque

we

the

brace

no-charge replacement. As soon as parts are available,

are in numerical

you

receive

is

(example)

and

1108,

1975

75-2)-

Fond

340

du

S(T,

to

No

440

which

. 75-4

SfT

and

the

block

(11

122/74)

440

is

subjected.

Box

you

received.

load and stress

recommend construction and installation
block.

is

in

process and will be available soon for

details

will follow

in

a later bulletin.

T

fT

of

Models

a

Figure

Support

Brace
Installed

2.

Sup

: Al

•

port

Brace

uminum

Figure
Cracked
Pillow
Block

14" Long

l"Wide

lja"Thick

1.

09009