Mercury 1976 340 s/t Reference manual

Number: 76-9

Date :

12/1/75

SNOWMOBILES

CIRCULATE

SERVICE MGR. PARTS MGR. MECHANICS

TO:

GASOLINE/OIL RECOMMENDATIONS -

ALL MERCURY SNOWMOBILES

(Atwch

Bulletin Reference Sticker to

Page

1-6

of

Your Snowmobile Service Manual.)

IMPORTANT: Supersedes all information previously published

on

gaso-

line/oil recommendations: Service Manual, Operation and Maintenance

Manuals, Snowmobile Service Bulletins and "FuelWarning Tags- Posters".

Fan Cooled and Free-Air Models

Fan

Cooled Free-Air

Place in Your

"Service Bulletins

Binder

Recommended Oil(s) Ratio (1) Gasoline (2) Ratio Gasoline (3)

Quicksilver Snowmobile 50:1 Regular 20:1

Quicksilver Formula 25 50:1

Leaded

20:1 100/130

Quicksilver Formula

500

50:1 Minimum

86

20:1 AvGas

Quicksilver Formula 50 50:1 Average Octane 20:1

BIA!TC-W Rated 40:1 (80

Motor

Octane) 20:1

(1) Ratio

of

25:1

is required

for

the

first

(one)

tank-full

duringengine

"Break-In"

period

and/or

for

"Severe Service" operation. Refer

to

;,/Operation andMaintenance

Manual"

for

;,/Severe

Service"definition.

(2)

For

1975

Model440

TIT

(Below CHASSIS Serial No. 4210250),

use

PREMIUM, UNLESS

ignition

timing

is retarded

from

.095"

BTDC

to

.080"

BTDC.

(3)

For

Racing,

use

100/130 AvGas and retard ignition

timing

from

.100"

BTDC

to

.080"

BTDC.

For

Trail Ride,

use

PREMIUM

andretard

ignition

timing

from

.100"

BTDC

to

.060"

BTDC.

Liquid Cooled Models

Recommended Oil(s) Liquid Cooled

Ratio Gasoline

Quicksilver Formula

50

20:1

Quicksilver Snowmobile Oil 16:1 100/130 AvGas

Quicksilver Formula

500

16:1

BIA!TC-W Rated 16:1

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

a

20:1

ratio. Use

of

these prediluted

oils, ONLY,

at

a 16:1 ratio are permissible. CHANGE any

of

these Manuals

to

the above recommendation (16:1 ratio).

r:

/tS-Tz-

~I:KYI~~

TIIEI#'L

ZIN'Y

SNOWMOBILES

Date :

12/15n5

BULLETIN

n

~~P.J

CIRCULATE

SERVICE MGR. PARTS MGR. MECHANICS

6

..

...

~-=·

TO:

oe

wt"•"d""'

-KO

A. Balancer Installation- 1976 Model340

Strand

440

Str

Snowmobiles

B.

Driv

e Clutch Weights-

AU

1976 Model340

Str

C.

Driv

e Outch Weights-

AU

1976 Model440

Str

D. Lower

Cowl

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

A.

BALANCER

INSTALLATION

-1976 Model

340

S(f

and 440 S/T Snowmobiles

(Attach Bulletin Reference Sticker

on

Section

2C

In.dcx

Page

of

Your Snowmobile Service Manual.)

For

ALL

1976 Model

340

S(f

(CHASSIS Serial No. 4495560

and

Above)

For

ONLY

1976

Model440

S(f

(CHASSIS Serial No. 4349537

and

Below)

IMPORTANT: ALL 1976 Model250

SIT

already are equipped with the balancer.

Place

in

Your

"Service Bulletin!

Binder

ALL 1976

Me

rcury Sno-Twister Snowmobiles

MUST

BE equipped with a balancer (steel disc

.156"

[3.96mm] thick by

5.250"

[l3.34cm]

diameter) between the rewind starter cup and lower pulley.

The balancer (D-75961) stabilizes the crankshaft and prevents excessive vibration of the drive

clutch, thereby improving the life

of

drive clutch components.

IMMEDIATELY notify owners

of

the above specifi

ed

Sno-Twister Snowmobiles

that

this balancer

MUST

BE INSTALLED (installation instructions following).

IMPORTANT: A simple visual inspection via the water pump belt channel in the bell housing

can verify whether-or-notthe balancer has been installed.

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 will be issued

upon receipt

of

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

Nos

.) may be used to cover service

to

all snowmobiles.

C-75961

C-10-75967

INSTALLATION

INSTRUCTIONS

l.

Remove rewind starter assembly.

Balancer

(1

per Snowmobile}

Scre

ws

(4 per Balancer)

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

er

pulley

to

rotor. RETAIN

th

e 4

lockwashcrs from the screws and discard the screws.

3.

In

sl

all balancer between lower pulley and s

tart

er rewind cup.

IMPORTANT: Failure

to

use the 4 lockwashers

on

the 4

NEW

retaining screws

will

result in

damage

to

the rotor and could alter ignition timing.

a. Place MACHINED side of balanc

er

against lower pulley (toward engine).

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

NEW

screws, apply Loctite Type

"A"

(C-92-32609)

to

threads

of

screws and reinstall starter rewind cup with screws.

4. Reinstall rewind starter assembly.

(OVER)

B.

DRIVE

CLUTCH WEIGHTS-

ALL1976

Model340 SIT

(Attach Bulletin Reference Sticker on Section

2C

Index Page

of

Your Snowmobile Service Manual.)

ALL 1976 Model

340

Sff

Snowmobiles

MUST

BE equipped with

#135

weights (D-71737) in the

drive clutch assembly (6 weights per clutch). Some 340 SIT Snowmobiles (CHASSIS Serial No.

4495867 and Below) were shipped from the factory with

#106

weights in the drive clutch, and

these ARE NOT LEGAL for "Stock

II"

class racing.

To

remedy, IMMEDIATELY notify owners

of

1976

Model 340

Str

Snowmobiles to check the drive clutch for correct

#135

weights.

INSPECTION PROCEDURE

l.

Part No. stamped into perimeter

of

drive clutch cover, as follows:

INCORRECT:

XXXX

088

CORRECT : XXXX-988- or XXXX-989-

088 088

2. OR, visual inspection

of

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

as

follows:

INCORRECT:

XXXX

106 (Color- Red)

CORRECT :

XXXX

135 (Color- Black)

IMPORTANT:

If

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

assembly from the engine before attempting clutch disassembly. Removal and/or installation

of

the drive

clutch~

works best

-·

with the aid

of

an arbor press.

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

to

all snowmobiles.

D-71737 Weight-

#135

(6 per Clutch Required)

C.

DRIVE

CLUTCH WEIGHTS-

ALL1976

Model440

SIT

(Attach Bulletin Reference Sticker on Section

2C

Index

Page

of

Your Snowmobile Service Manual.)

ALL 1976 Model

440

Sff

Snowmobiles

MUST

BE equipped with

#106

weights (D-71717) in the

drive clutch assembly (6 weights per clutch). Some

440

SIT Snowmobiles (CHASSIS Serial No.

4349543 and Below) were shipped from

the

factory with

#123

weights in the drive clutch, and

these ARE NOT LEGAL for "Stock

ill"

class racing.

To

remedy, IMMEDIATELY notify owners

of

1976 Model440 SIT Snowmobiles

to

check the drive clutch for correct # 106 weights.

INSPECTION PROCEDURE

l.

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

INCORRECT:

XXXX

089

CORRECT :

XXXX

-989-

089

2. OR, visual inspection

of

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

as

follows:

INCORRECT:

XXXX

123

(Color-

Yellow)

CORRECT :

XXXX

106

(Color-

Red)

IMPORTANT:

If

the

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

assembly from the engine before attempting clutch disassembly. Removal and/orinstallation

of

the drive clutch cover works best

--

with the aid

of

an arbor press.

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

~os.)

may

be

used

to

cover service

to

all snowmobiles.

D-71717 Weight-

#106

(6 per Clutch Required)

D. LOWER COWL

and

SNOW FLAP

FASTENERS-

ALL

1976 Model 250-340-440 Sno-Twister

Snowmobiles

(4ttach Bulletin Reference Sticker

on

Section

2F

Index

Page

of

Your Snowmobile Service Manual.)

LOWER COWL

To be sure

that

the lowf'r cowl remains securely fastened

to

the front crossmember,

we

recommend

that

th<>

6 aluminum rivets, which secure

th

e cowl

to

the

front

crossmember (silver colored,

5/8"

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

of

crossmember), be replaced with

STEEL rivets (Mercury Part

No

. C-17-76047)

or

an equivalent steel riv

et

(3/16"

[4.8mm]

diameter

shank X 5

/8"

[15.9mm) diameter head with

3/8"

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

SNOW FLAP

Check the rivets which secure the snow flap and mounting

str

ip

to

th

e chassis.

To

prevent

the

rivet

from pulling

out

thru the snow flap, make sure

that

the

"clinch"

end

of

the

ri

vet (inside

the

tunnel)

has a

"backing"

washer on

<>ach

riv

et

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

(13/64"

[5.16mm] J.D. x

Y2"

[l2.7mm]

O.D. x

l/16"

[l.59mm]

thick).

If

the

rivets arc

not

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

or

equivalent) with the backing washers.

0

.J'

~I:KY

l\;1:

TIIEH

SNOWMOBILES

Number: 76-13

Date : 12/22/75

B

ULLETIN

I

~

~!!",&

CIRCULATE SERVICE MGR. PARTS MGR. MECHANICS

Place

in

Your

701.11

Ul\lf•I'IC•

"Service Bulletins

of

<WI$l.nd1t19 TO:

.......

MERCURY SNOWMOBILES with ARCTIC DRIVE CLUTCH

Internal Drive Clutch Component Information

"Stock"

Drive

Clutch

Component

Chart

1975 1975 1976 1976 1976 1976 1976

MODEL

NAME

340

srr

440S

/T 340 TIT 440 TIT 25o

srr

340S!T

440

srr

CHASSIS Serial No. Below Below Below Above Below Above Above

4207500 4206250 4347125 4347124 4495560 4495559 4349324

MERCURY PART

NO

. D-52-71571 D-52-71572 D-52-74255 D-52-74256 D

-5

2-75098 D-52-75099 D-52·75100

LAST 3 DIGITS

of

NO. STAMPED ON 061 062 077 080

081

088 089

OUTSIDE

of

DRIVE

CLUTCH COVER

DRIVE

CLUTCH SPRING

Color Blue Blue Blue Blue Green

Green

No.

of

Turns 3.9 3.9 3.9 3.9 5.0 5.0 5.0

Mercury Part No. C-24-71517 C-24-71517 C-24·71517 C-24-71517 C-24-74992 C-

24

-7

4992 C-24-74992

DRIVE CLUTCH WEIGHTS

Color

Red

Black

Red

Yellow

Red

Black

CD

Red

No. Stamped on Weights 0146·106 0146·105 0146-106 0146-286 0146·106 0146·135CD 0146-106

Gram Weight 5.958g 7.858g 5.958g 8.800g 5.958g 4.479g 5.958g

Outside Diameter

0.530" 0.598"

0.530"

0.629"

0.530" 0.471" 0.530"

Mercury Part No. D-71717 D-71716 D-71717 D-74125 D-71717 D-71737

CD

D-71717

DRIVE CLUTCH RAMPS

No. Stamped on Ramps None None 292 293 None None None

Drawing

of

Ramp Profile Figure 1 0 Figure 1 0 Figure 3 Figure 4 Figure 5 Figure 6 Figure 6

Mercury Part No. D-71496 (!) D-71496 (! D-74123 D-74124 D-75908 D-75177 D-75177

CD

Optional Clutch Ramps (D-74857A

1,

Figure

2)

are available

for

trailriding.

Q)

A few 1976 Model

340

SIT

snowmobiles were shipped from the factory

with

INCORRECT

drive clutch weights. Weights stamped 0146-135 (D-71137)

MUST

BE

INSTALLED

in

these

clutches.

: :

..

-

ACTUAL

SIZE

'

·'

/

l J

/

ACTUAL

SIZE

ACTUAL

SIZE

Binder

Figure 1. D-71496 Drive Clutch

Ramp Profile (1975

340

S/T

&

440

S/T)

Figure

2. D-74857A1 Drive

Clutch Ramp Profile (Trail Ramp

for

1975

340

S/T

& 440 S/T)

Figure 3. D-74123 Drive Clutch

Ramp Profile (1976

340

T/T)

(OVER)

ACTUAL SIZE

Figure

4.

D-74124 Drive Clutch

Ramp

Profile (1976 440 TIT)

ACTUAL SIZE

Figure 5. D-75908 Drive

Cluttch

Ramp

Profile (1976 250 SIT)

Drive

Clutch

Accessories

1975 1975 1976 1976

ACTUAL

SIZE

Figure

6.

D-75177 Drive Clutch

Ramp

Profile (1976 340 SIT &

440 SIT)

1976 1976 1976

MODEL

NAME

340

SIT

440S/T

340

TIT

440

TIT

250

SIT

340

S/T

440SIT

Drive Clutch Elevation

Kit

D-71712A1 D-71712A1 D-74124A1 D-i11716A1 D-71712A2 D-71712A2 D-71712A2

Drive Clutch Modification

Kit

D-71711A1 U-71711A1 N.A. N.A. D-71711A2 D-71711

A2

D-71711A2

Drive Clutch Trail Ride

Kit

D-74857A1 D-74857A1 N.A. N.A. N.A. N.A. N.A.

N.A. -

Not

Available

Drive

Clutch

Weight

Chart

I

Full

Throttle

No. Stamped Outside Diameter

Engine

RPM

Gram Weight on Weight Color

of

Weight

of

Weight Part No.

Increase

light

3.058g 0146-108

CD0

Yellow

0.406"

D-71731

CD

0

Engine

RPM

3.725g 0146-175

CD0CD

Red

0.437"

D-71735

CD

0

CD

4.479g 0146-135

CD0CDCDCD

Black

0.471"

D-71737

CD

0 Q)

CD CD

4.958g 0146-107

CD

White

0.491"

D-71736 Q)

CD CD

5.958g 0146-106

CDCD

Red

0.530"

D-71717

6.992g 0146-123

CD0CD

Yellow

0.568"

D-71734

Decrease

7.858g 0146-105

CD

Black

0.598"

D-71716

Engine

RPM

Heavy 8.800g 0146-286 0 Yellow

0.629"

D-74125

Q)

Six

of

these

weights are included

in

Drive Clutch

Modificat~on

Kit

(D-71711A 1

).

@ Six

of

these

weights are included

in

Drive Clutch

Modificat~on

Kit

(D-71711A2).

G)

Six

of

these

weights

are

included

in

Drive Clutch Elevation ,Kit (D-71712A

1).

Q)

Six

of

these

weights

are

included

in

Drive Clutch Elevation

Kit

(D-71712A2).

(D Six

of

these

weights are included

in

Drive Clutch Elevation

Kit

(D-71716A 1

).

CD

Six

of

these

weights

are

included

in

Drive Clutch Elevation

Kit

(D-74124A

1).

CDCD

CD0CD

CD

0

5NU•TWISTER

TIPSTER

HI-PERFORMANCE

NO.

74-1

INTR

OD

UCTION

(Flash 'Inside'

Info

for

MercurySnowmobile Dealers

to

Z-i-p

to

Their Sno-Twister Customers)

11/16n3

It's

official!

After

months

of

spinning on hay

and

straw,

or

on

just

plain

grass,

the snowmobile

season

-on good old Alaskan snow -

has

opened

with

a resounding

"Margin

for

Mercury".

Eager

sponsor

of

the

kick-off

race meeting on

Nov

..3rd and

4th

was Brandt's Lodge

...

and,

if

you're

real

quick

in

geography,

you'll

find

it

160 miles northeast

of

Anchorage. Give or take a couple

of

months,

that

can

be real mean blizzard

territory.

Ignoring all impending hazards, however, were

local drivers

who

had

"WIN"

written

all over

their

Sno-Twisters.

The Sno-Twisters leaped

to

the

front

and stayed there

to

win

all three heats in

their

400

class,

plus

the final around the oval, all on Saturday. Then Sunday the crew came

right

back

to

grab

first

place

honors

in

cross-country.

So, here's the bonus! We,

of

course, are happy

to

share

the secrets

of

success

so

that

you,

too,

can

make the run

for

the

roses.

The

following

procedures were

used

in setting-up the champion

Sno-Twisters at Brandt's Lodge:

ENGINE

1. Check

timing

@3000 RPM

.100"

.±.

.005"

BTDC.

2.

Adjust

idle slow enough

to

allow

clutch

to

reset. (Too high idle

speed

will

cause

partial

engagement and

belt

drag, resulting in a slower start

off

the line.)

3. Check

for

proper jetting.

The

following

jet

sizes

will

serve

as

a guide, however, a proper plug check

is

the

only

way

to

get

spot-on

for

racing. A Champion N55G plug

is

easier

to

read

and

is

suitable

for

racing.

(After

100 yd.

full

throttle

speed

run, the correct

fuel/air

mixture

will

cause

plug electrode

to

have

a

light

chocolate brown

color-

must never appear whitish/grey.)

BELOW 2000'

ELEVATION

Temperature

Above

300

0.

3QO

Below

oo

Jet Size

290

to

300

320

to

330

to

360

2000'

to

4000'

ELEVATION

Subtract 10

from

the

jet

sizes

Iisted on left.

If

your

Mercury dealer doesn't

have

jets,

try

any dealer stocking

Mikuni

carburetor parts.

If

all

else

fails, a

#53

drill

(.059 dia.) corresponds

to

a

320

jet, and a

1/16

drill

(.0625 dia.) corresponds

to

a

340 jet.

Move

jet

needle

to

richer position

by

one notch; i.e. the retaining

clip

should be moved

to

the

fourth

(4) notch

from

the

top

of

the

jet

needle.

DRIVE

SHEAVE

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

and

Maintenance

Manual"

(C-90.68019).

2. Check engagement

RPM

and adjust

if

necessary.

3.

Use

an

accurate tachometer

to

check engagement

speed.

(USSA

says

4000

RPM

max.)

(OVER)

DRIVEN

SHEAVE

1. Check alignment per the manual.

2. Set spring preload

at

2

full

cams.

3. US!: A NEW

BELT.

4.

Adjust

belt tension per the manual.

FUEL

OIL

Use

a 20:1 fuel-oil

mix.

Only

the

following

oils are known

to

be

satisfactory

for

SNO-TWISTER:

Mercury Formula 25 Mercury Formula

50

Mercury Formula

500

Castrol Synthetic High Performance Snowmobile Oil

NOTE:

You

may

want

to

clamp

or

wire the fuel lines

at

the fuelpump.

ICE STUDS and

CARBIDES

Carbide wear

skegs

(D-68440) must

be

installed

for

racing. The ski holes may need

to

be

drilled

out

and

an

oversize washer

used

above the ski

to

make the carbide

fit

properly.

Ice studs (D-68441) must be installed on the track. A good starting

point

is

to

install eleven studs

on each side,

utilizing

the holes in the track bars. One

or

two

additional rows

of

eleven

can

be added

in the center band

of

the track

but

should be attached

to

the rubber

only,

not

thru

the bar.

Use

washers

to

space

the studs

up

to

the

3/8"

allowable.

You

may prefer

to

set the steering in the

low

effort

position, since the carbides increase the steering

effort

considerably.

See

your

"Operation

and

Maintenance Manual".

SLIDER/TRACK

ADJUSTMENT

The track must be adjusted

for

proper tension

as

outlined in

your

Owners Manual. The track

will

run smoother

if

the drive sprockets

are

lubricated

with

grease

(STP

works well). Most

of

the side

load

is

taken

out

through the wear plates inside the tunnel,

so

be

sure

to

lubricate the

edge

of

the

track.

As outlined

in

your

Owners Manual, handling (oversteer and understeer)

can

be

adjusted.

We

found

that

for

best

weight

transfer, the rear springs should be

set

soft

and the

front

springs

in

the %

position. Set yours

up

and test

prior

to

racing.

TETHER

SWITCH

Disconnect

on-off

switch wire

from

#3

stud

of

terminal block,

to

prevent accidentally stopping the

engine.

Attach

a paper

clip

to

the tether switch cord

and

hook

the

clip

on the

throttle

cable

so

that

the clip

must be pulled free before the tether is disconnected.

Check the tether switch operation. Moisture

will

cause

the points

to

freeze, resulting in a switch

malfunction. Gasoline de-icer

will

eliminate the moisture.

COWL

The aluminum hinge rivets should be replaced

with

large

head

steel rivets

or

bolts. The headlight

should be removed

or

taped

and

the screws secured

with

silicone sealer.

**IMPORTANT

NOTE:

U.S.S.A.

has

ruled

that

we cannot

use

the boggie wheel

kits

for

racing.

S

no-

TwisterI

Hi-Performance

Tipster

No. 75-1 (6/1174)

Important

Info

about

Snowmobile

Registration

and

Sno-Twister/Hi-Performance

Tipster

Mailing List

Mercury Marine

is

introducing

another

FREE

customer

benefit:

Owner

direct

mailing

of

the

new

"Sno-Twister

/Hi-Performance

Tipster",

aimed

primarily

for

racing machines.

To

get

the

project

in

gear

,

the

following

"IMPORTANT"

Tipster

mailing list directive will

be

included

in

the

"Snowmobile

Information"

envelope

shipped

with

all Mercury

Snowmobiles

manufactured

after

Sept.

1,

1974.

IMPORTANT

MR. DEALER -Mercury Marine has

made

an

important

change

to

Snowmobile

Registration Cards. We've

added

RACING0to

the

"Primary

Use" section

of

the

card.

We've

done

this

in response

to

many

requests

from

owners

(primarily use

their

snowmobiles

for

racing)

who

wish

to

receive,

from

the

factory,

owner

direct

mail

of

latest

information

in "Sno-Twister/Hi.Performance

Tipster"

bulletins

on

racing.

To

compile

such

a

customer

mailing list via

direct

computer

mailing,

it

is ESSENTIAL

that

1)

you

fill

out

all registration cards, 2)

you

ascertain

from

the

owner

the

primary

use

intended

and

mark

the

registration

card

accordingly

and

3)

you

promptly

mail all cards

to

the

factory.

We're sure

that

every racing

owner

will

want

to

take

advantage

of

this

FREE.

direct

mail

service.

Only

you

can

get him

on

the

racing

"Tipster"

list! If

he

races,

check

RACINGD.

C-90-71050

(5

174)

We'll

also

advise

owners

in

their

"Operation

and

Maintenance"

manual

that,

if racing

is

intended,

it

should

be

properly

checked

on

the

new

machine's

Registration Card

under

RACING 0

so

that

the

customer

will

be

mailed

the

"Tipster"

bulletin.

This

"Tipster"

sheet

will

be

used exclusively

to

notify

owners

of

high

performance

information

and

time-saving tips.

IMPORTANT:

The

service is

intended

strictly

as

an

owner

benefit.

Dealers still will receive

an

identical

mailing

at

the

same

time.

Sno-

TwisterI

Hi-Performance

Tipster

NOTICE:

Sno-Twister/Hi-Performance

"Tipsters"

are in numerical

order,

starting

with

75-1.

If

the

first

copy

you

receive is

(example)

75-3

•·

and

you

desire

issues (75-1

and

75-2) -

advise

Mercury

Marine

Publications

Dept.,

P

.0.

Box

1108,

Fond

du

Lac,

WI

54935.

and

give

the

first

number

that

you

received. No. 75-2

(11

120174)

1975SNO-TWISTER- (340

S(T-

440

S(T)-

COMPETITION SETUP INFORMATION

POSSESSION

Possession

of

a Sno-Twister well

in

advance

of

the

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

It

gives

the

driver ample time

to

get acquainted with

the

sled and

to

properly break it

in

before entering

competition.

INITIAL SETUP

After receiving a Sno-Twister,

you

may

want

to

thoroughly check

the

engine assembly and possibly

even disassemble

it

completely

to

familiarize yourself with

all

the

parts and

to

make certain

that

all

components and

their

assemblies meet with your satisfaction.

If

so, rebuild

the

engine with

the

care and

precision

that

a surgeon would use.

It

brings results!

• Pay special attention

to

all

nut

and

bolt torque specifications.

Use

"loctite"

on

all bolts

that

secure trigger and

stator

to

crankcase.

• When assembling cylinders

to

crankcase, make sure

that

the

transfer ports are lined

up

correctly,

with

no

gasket overhang. Make certain

that

the

cylinder head

dome

is

centered directly over

the

cylinder.

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

to

specifications.

• Reinstall engine assembly, then check

torque

converter alignment, drive

belt

tension, drive chain

tension, track tension and alignment and adjust

to

specifications (refer

to

Owner's Manual).

BREAK-IN PERIOD

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

is

advisable.

Use

a good premium gasoline and Mere Snowmobile

Oil

when mixing gas/oil. Make

it

a slightly richer

mixture for

the

first few hours

of

running (until piston rings have seated properly). Run

at

high

RPM

for

short

durations only --avoid sustained full

throttle

operation and prolonged operation

at

a

constant

throttle

setting. Check spark plugs often

to

ensure

that

engine

is

not

overheated.

Become familiar with

the

feel

of

the

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

characteristics. This

is

very important

for

later testing.

RACE PREPARATION (BASIC)

Cleaning and Inspection: After

the

break-in period

is

completed, thoroughly clean the snowmobile.

Visually check

the

engine and chassis for worn

or

broken parts. Remove cylinder heads and inspect

head gaskets, pistons, rings and cylinders for excess wear, cracks, chipped chrome, etc. Repair

or

replace

components as necessary. Check piston

fit

and ring clearances (end gap and side clearance).

Secure exhaust headers

to

cylinders, using safety wire

or

bearing

mount

type

"Loctite"

on

hex screws.

Check ignition timing (should

be

.100"

BTDC [21%0]

).

Check ski alignment (parallel, measuring

front

and rear

of

skis).

For

easier (slower) steering, use

the

tie

rod attaching hole closest

to

the

steering shaft.

Try

both

positions for

your

preference.

Check track and suspension: Track tension

and

alignment, suspension cross shafts (wear/bending -

lubrication), shock absorbers (dampening/leakage), idler wheels (wear and free bearing movement), slide

wear bars

and

chassis

rub

strips. Check all

nuts

and bolts for wear

and

proper

torque.

Repair

or

replace

parts as necessary.

Chaincase: Clean

and

inspect chain, sprockets, jackshaft and bearings.

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

"free

floating" and correctly adjusted.

RACE PREPARATION (FINAL)

Check electrical wiring: Disconnect emergency

stop

switch (red switch

on

throttle

control)

from

terminal block (located behind dash). Be sure

that

ground wire from

CD

mounting base

to

engine is

secure and in good condition. Red wire from electronic pack

connects

to

PTO side coil; white wire

connects

to

coil

on

rewind side. Make certain

that

CD

wiring connectors are coupled securely.

Install a "race-proven" ignition safety

stop

switch (tether switch)

to

suit rider. Check

and

adjust

carburetion; re-check

carburetor

float levels. Adjust high speed mixture needles (as outlined

in

Owner's

Manual)

to

suit

conditions (temperature

and

elevation)

that

will

be

encountered. Synchronize

throttle

slides and adjust idle speed, making sure full

throttle

operation

is

attained and

throttle

cable moves

freely. Check all fuel lines

and

hoses.

Be

positive

that

the

lines are secure

on

fittings and

not

pinched

or

crimped.

Check

exhaust

system: Inspect

for

cracks, broken parts

and

missing coupler springs. Make certain

that

system is mounted securely.

Drive sheave (clutch): disassemble

and

clean. Check fiber bushings

in

movable and fixed sheaves for

wear

and/or

binding. Check all moving

parts

for wear and restricted movement. Make sure

that

ramps

are properly seated in movable face. Engagement

RPM

can

be

raised

by

adding spacers

on

spring

or

lowered

by

removing them. No

more

than

four

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

be sure

to

match alignment mark

on

movable sheave with mark

on

sheave cover

and

take

care

not

to

bind fiber

bushing-

no

lubrication is necessary.

Driven sheave: Disassemble and clean. Check condition

of

torque

bracket wear plates. Replace if

necessary. Reassemble

and

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

required (approximately 2 ramps)

to

attain maximum recommended

RPM

at

wide open

throttle

(8250

RPM)

-refer

to

Owner's Manual.

Torque converter alignment: Check

and

adjust alignment (parallel

and

offset

distance between sheaves).

Inspect drive belt

for

wear, distortion,

burn

spots

and

cracking. Check drive

belt

tension. If

in

doubt

about

condition

of

belt,

replace

it-

refer

to

Owner's Manual.

Drive chain: Drain and refill chaincase

with

3 oz. (3.1 imp. oz.)

of

automatic transmission fluid (ATF).

Check

and

adjustchain tension

to

specifications.

Suspension adjustments: Understeer and oversteer can be varied

by

changing spring tension on

front

cross shaft. Rear shocks can

be

adjusted for firm

or

soft

ride, depending upon rider preference. Best

weight transfer requires a

soft

settin9

at

rear-

refer

to

Owner's Manual.

Track/slide suspension alignment: Align track

first

to

slides, then

to

chassis

tunnel.

NOTE: Because the front control arm always is

in

compression,

it

may

be

necessary to rework the

suspension mounting holes slightly

and

adjustalignment with the suspension bolts loose in order to

achieve

perfectalignment

of

the

slider

suspension

inside

the

chassis

tunnel.

Traction devices: Three types

of

studs

are

available

from

Mercury Marine

for

various types

of

racing

surfaces

and

conditions.

D-68441

D-71925

D-71926

Mere Stud (22

Pes.

Per

Package)

Mere Scat Stud (22

Pes.

Per

Package)

Mere

Carbi•tle

Stud (22

Pes.

Per

Package)

Placement and pattern

are

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

rivet in the outside

ends

of

each

track bar

can

be

removed,

if

absolutely

necessary,

to

place a stud.

Track lubrication: Lubrication

of

the track

can

be

beneficiial

by

reducing drag between track

and

sides

of

tunnel and between drive sprockets

and

track.

(STP

lubri•cant workswell.)

Skis/carbide wear

skegs:

Carbide wear

skegs

are

a MUST

for

stock racing and

are

available

from

Mercury

Marine.

D-68440-1

D-71334 Carbide

Sk•eg

{Pair-

10"

Carbide Inserts)

Carbide

Sk•eg

(Pair -

6"

Carbide Inserts)

Badly chipped, bent

or

broken carbide

skegs

should

be

replaced immediately. Placement

and

length

of

carbide

skegs

influence handling

to

a high degree and, again,

are

mostly rider preference.

Special application:

At

this

time, the following equipment

is

available

from

Mercury Marine

for

special

application; i.e., high elevation,

cross

country

racing and modified racing:

D-1393-5872A1

D-1393-5854A1

D-71712A1

D-71711A1

C-58601A1

High

Eleva1tion

Carburetor

Kit

-340

S/T

High

Eleva1tion

Carburetor

Kit

•

440

SIT

High

Eleva1

tion Drive

Sheave

Kit

-340

SIT

and

440

S/T

Modified Drive

Sheave

Kit-

340

SIT and

440

SIT

Bogie

WheEl!

Kit

-

340

SIT and

440

SIT

DriverSprockets {340

SIT

and 440 SIT)

prive

Chain {340

SIT

and

440

S/T)

(1) D-69757-12 12

Tooth

(2)1

D-71483 78 pitch length

D-68439 13 Tooth

D-64684 14

Tooth

(2)1

78

pitch chain

must

be

used with

16

tooth

D-63318A1 15

Tooth

sprocket.

D-64131 16 Tooth

(1)

One C-23-69842 spacer

must

be

used with 12

tooth

sprocket.

CONCLUSION

The aforementioned steps

have

touched basically on major

aspects

of

setting

up

a 1975 Mercury

Sno-Twister

for

competition. Hard

work,

patience, thorouuhness

and

a strong desire

to

win can--

and

will--

produce a competitive Sno-Twister

that

will

win

consistently.

-

MERCURY MARINE -CERTIFIED SNOWMOBILE SPECIFICATIONS

M

ODEL

NAME

1974

SNO-TWISTER

ENG

IN

E SPECIFICATIONS

Engine Manufacturer Kohler

Eng

i

ne

Model K400-2RS

No.

of

Cylinders 2

Engine Displacement 398.2

Type

of

Cooling

FA

Bore 65.0

Stroke 60.0

Ignition CD

Min.

Compressed Head 0.95

Gasket Thickness

Min.

Compressed

Base

0.35

Gasket Thickness

~~olume

of

Head

to

Top

of

Spark Plug Hole 19.0

Crankcase Volume 290.0

Overall Length

of

Cylinder 109.0+0.01

Depth

-Top

of

Cylinder 90.5

to

Bottom

of

Intake Port

Depth·

Top

of

Cylinder 30.0

to

Top

of

Exhaust

Port

Depth-

Top

of

Cylinder 47.0

to

Top

of

Transfer

Port

No.

of

Transfer Ports 4

Width

of

Transfer Ports 32.0/11.7

Width

of

Intake Ports 46.0

Width

of

Exhaust Ports 40.0

Height

of

Transfer Ports 13.0

Height

of

Intake Ports 29.0

Weight-Piston Assembly

300gr.:!:,20gr

Complete

Overall Height

of

Piston 71.7

No.

of

Rings per Piston 1

Ring Type L-Ring

Ring Thickness 2.0

Crankcase

Face

to

Center 70.0

of

Crar>kshaft

Main Bearing

Type

Sea

led-Ball

Muffler

Make Mere/Donaldson

DBA

Level 82+2

Head Pipe Length 98.5

<D

Piston @

TDC

NOTE:

All

length

Measurements Are in Milli

meters

, unless

Spec

ifi

ed

Inches

(");A

ll

Volume Is in C

ubic

Cent

im

ete

rs (Conversion Table Below).

1975 1975 1975 1975 1975

340

S/T

440S/T

440

TIT

340 S/R 440 M/X

Kohler Kohler Kohler Kohler

Kioritz

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

2 2 2 2 2

339.3 429.4 435.8 338.1 437.9

FA

Fa

n

Fan

60.0 67.5 68.0 62.0 66.0

60.0 60.0 60.0 56.0 64.0

CD CD CD

Mag

1.2 0,7

1.1

1.2

1.1

0.3

0.3 0.3

14.7 19.0

21

.7 17.7

21.4_±5%

305.0 305.0 630.0+10% 463.0+10% 931.0+10%

109.0±.5 109.0+.5 109.0 + .1/-.2 98.3+.2 115.95+.5

90.Q±1.5 95.3±1.5 92.0+.75/-1.0 84.3+.75/-1.0

Reed

Valve

29.5_±1.5 29.0_±1.5

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

37.5_±1.0

46.25±1.5

46.25.:!:,1.5

47.8+.6/·1.2 43.8+.6/-1

.2

51.5.:!:,1.0

4 4 4 2 4

33.0.:!:,1.5/

33.0+1.5/ 35.0+1.0/

27.0.:!:,1.0

85.0_±2.0

12.5±1.0

13.0

;!:

1.0 13.7+1.0

45.0+1.5 43.0+1.5 48.0+1.0 37.0+1.0 Reed Valve

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

14.0+1.0 14.0+1.0 13.7+1.0 14.0

:!:_1.

0 13.5+1.0

28.5+1.0 30.3+1.0 24.0+.5 22.5+.5

Reed

Valve

240gr;!:10gr 310gr

;t

10gr 335gr;t10% 240gr;!:10% 307gr±10%

67.5+.55

70.7+.5~

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

1 1 2 2 2

Dykes Keystone Dykes Keystone

"L"

& Rectangular

"L"

& R,ectangular Rectangular

2.0+.08 2.5+.08 2.0+.08 2.0+.08 1.5+0.1

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

Sealed-Ball Sealed-Ball Sealed-Ball

Sea

led-Ball

Sea

led-Ball

Mercury Mercury Mercury ACS Cowl

82+2 82+2 82+2 82+2 82+2

117.0+2 167.6+2

"Y"-Manifold

24.5"+.25"

15.25"+.25"

1975 1975

440 S/R

Markll

Kioritz

Mercury

KEC-440/22

Markll

2 2

437.9 644

Fan Fan

66.0 79.37

64.0 65.07

Mag

CD

1.1

N.A.

0.3

N.A.

21.4:!_5%

28.5

931.0+10%

N.A.

115.95+.5 174.62

Reed

Valve Boost • 53.08

37.5_±1.0

39.11

51.5.:!:,1.0

50.80

4 2

85.0.:!:,2.0

35.05

Reed

Valve Reed Valve

40.0+1.0 47.0

13.5+1.0 20.32

Reed

Valve Reed Valve

307gr:!:_10%

491.68gr

71.42+.5 75.41

2 3

Rectangular Cast Iron

1.5+0.1 1.57

70.23;!:.2 1-Piece

Sealed-Ball Sealed-Ball

Cowl Mercury

82+2 82+2

15.25";!:.25" 127.0

~

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

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.........::

CARBURETOR

Make/Model No.

MikuniNM·36

Mi

kuni/36/34RS

Mikuni/36/44RS

MikuniNM

·36 Walbro/WDA·50 Walbro/WDA-47 Walbro/WDA-47 Walbro/WRA-3

No.

per

Engine 2 2 2 2 1 1 1 2

Venturi -Smallest 36.0 36.0 36.0 36.0 39.7 39.7 39.7 32.5

Diameter in

Throat

Throttle

Bore -Largest Dia. 37.0 36.12 36.12 36.1

41.3

41.3 41.3 38.1

Downstream

of

Butterfly

Choke Yes Yes Yes

Yes

Yes Yes Yes Yes

DRI

VE

C

LU

TC

H

Arctic

Cat/

Arctic

Cat/

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

XXXX-062

Salsbury/850 Salsbury/850 Salsbury

/850

Mercury Salsbury/850

Engagement Speed 3800-4000

RPM

2)

4000RPM Max.

2)4000

RPM

Max. 3300 RPM+10% 3500 RPM+10% 3500 RPM+10% 3400 RPM+10% 3200 RPM+10%

No.

of

Springs/Color 1/Red 1/Biue 1/Blue 1/Piain 1/Piain 1/Piain 1/Piain 1/Piain

Spring Wire Diameter 4.75 .1

92"

.192"

4.32 4.32 4.32 4.74 4.3

No.

of

Coils 4.8 3.9 3.9 5.4+.2 5.4+.2 5.4+.2 5.2+.2 5.4±.2

Arm/Roller

Weight 38.6gr+.5gr 18gr+1.5gr 22gr+1.5gr 50.08gr+.5gr 40.12gr+.5gr 43.86gr+.5gr 65.32gr+.5gr 51.32gr+.5gr

DRIVEN

CL

UTCH

Make/Model No. Comet/90D Salsbury/152110 Salsbury/152110 Salsbury/850 Salsbury/850 Salsbury/850 Mercury Salsbury

/850

Spring Wire Diameter 4.75

.192" .192"

4.88 3.96 3.

96

5.71 4.3

No.

of

Coils 6 6.25 6.25 6.25+.2 5+.2 5+.2 6+.2 7+.2

Ramp Angle

45°

41° 41°

350 320

32°

40°

32°

CHASSIS/SUSPENSION

Chassis

Model 66769 70729 70729 72006 66602/70238 68345 69869 66011

Suspension Slide Rail Slide Rail Slide Rail Slide

Ra

il Slide Rail Bogie Wheel Slide Rail Swing Frame

Chassis

Length 1880+6.3 2235+6

2235+6

2235+6 2209.8

+6

2247+6

2521

Ski Length 1000±6.3 952.5+3 952.5+3 952.5+3 1008.4+3 1008.4+3 1008.4+3 993.78

Ski Width 117+3.1 117.6+1.5 117.6+1.5 117.6+1.5 136.6+1.5 136.6+1.5 136.6+1.5 152.4

TRACK

Make Goodyear Goodyear Goodyear Goodyear Goodyear Goodyear Goodyear Mercury

Material Rubber/ Rubber/ Rubber/ Rubber/ Rubber/Grouser Rubber Rubber/Grouser Rubber

Steel Bars Steel Bars Steel Bars Steel Bars

Width 381+3.2 381.0+3/-1.5 381.0+3/-1.5 381.0+3/-1.5 387.35 387.35 387.35 431.8

Length -0 .D. 2820 2816.4+12.5 2816.4+12.5 2816.4+12.5 3072.4 3009.9 3072.4 3327.4

Track Drive Sprocket Teeth 9 9 9 9 8 8 8 8

CHA

lNCASE

Standard Drive Sprocket

No.

of

Teeth 15 14 15 17 15

17

18

16

Standard Driven Sprocket 34 34 34 34 36 36 28

36

No.

of

Teeth

Optional Drive Sprockets 13-14-16 12-13-15-16-17 12-13-14-16-17 12-13·14-15-16-18 12-13-14-16·17

-18

12-13-14-15-16-18 12-13-14-15·16·17 12·13·14-15·17·18

No.

of

Teeth

Optional Driven Sprockets N

.A.

N.A . N

.A.

28-36·38-40 28-34·38-40 28-34-38-40 34-36·38·40 28-34·38·40

No. of Teeth

SnowmobileWeight(Pounds 360+10 365 365 365 350 390 380 500

METRIC CONVERSION: 1mm (millimeter) =

0.0394"

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

1

cc

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

b.

(pound) = 0.4536kg (kilogram)

NA.

a

Not

Applicable

(D

0-4 Spacers (.06Thick)

to

Achieve 4000 RPM Max.

Sno-

TwisterI

Hi-Performan

ce

Tipster

NOTICE: $no-Twister/Hi-Performance

"Tipsters"

are in numerical

order,

starting

with

75-1.

If

the

first

copy

you

receive

is

(example)

75-3 ••

and

you

desire previous

"Tipster"

issues (75-1

and

75-2)-

advise Mercury Marine Publications

Dept.,

P.O.

Box

1108,

Fond

du

lac,

WI

54935,

and

give

the

first

number

that

you

received.

No

. 75-4

(11

122/74)

Driven

Shaft

Pillow Block -

1975

340

S(T,

440

SfT

and

440

T

fT

Models

We

have received a few reports

that

the

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

crack (as shown

in

Figure

1)

because

of

the

torque

load and stress

to

which

the

block

is

subjected.

Thus far, complete breakage has

not

occurred.

At

this time, and only

as

a temporary measure,

we

recommend construction and installation

of

a

support

brace (as shown in Figure

2)

to

reinforce

the

block.

A new, stronger pillow block with a

support

brace

is

in

process and will be available soon for

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

deta

i

ls

will follow

in

a later bulletin.

Figure 2.

Support

Brace

Installed

•

Figure

1.

Cracked

Pillow

Block

Sup

port

Brace

: Al

uminum

14"Long

l"Wide

lja"Thick

09009

Mercury 1976 340 S/T Reference manual

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