arctic cat 1973 owners manual

1973 EXTForm No. 2254-023

Model No. 0250-022 (340)Model No. 0250-024 (440)Model No. 0250-026 (650)

• I OPERATOR'SMANUAL

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Printed December 1972Arctic Enterprises, Inc.

Thief River Falls, Minnesota 56701

TABLE OF CONTENTS) Page Page

Safety Tips . 1 Brake 16

Registration. 2 Drive Pulley. 16.Supplemental Parts 2 Driven Pulley 17

340 Specifications 4 Drive/Driven Pulley Offset 17

440 Specifications 5 Drive/Driven Pulley Center Distance 17 - 18

650 Specifications 6 Drive Chain 18 - 19

Fuel Mixing. 7 Drive Belt 19

Pre-Operating Safety Checks 8 Suspension 19 - 20

Break-In Procedure . 8 Track Tension 20

Starting Instructions 8-9 Track Alignment 20 - 21

Auxiliary Rope Starting . 9 Ski Alignment . 21

Maintenance and Adjustments 10 - 22 Fuel Filter 21 - 22

Check Before Each Race . 10 Spark Plug 22

Carb., Throttle and Synchronization 10 - 11 Trouble Shooting 23Carburetion (Fine Tuning) 11 - 14 EXT Identification 24

Carburetor Specifications 14 Maintenance Log. 24""t':- Lubrication . 15 - 16......

SAFETY TIPS1. Before the engine is started the operator

should, for safety purposes, wear the pre-scribed safety clothing and equipment.

2. Before the engine is started, check and insurethat the throttle lever is operating properly.A frozen throttle could cause serious bodilyinjury and/or damage to the snowmobile.

3. After the engine has been started, insure thatthe emergency shut-off switch located aheadof the right handgrip will operate properly.

5. Gasoline is highly flammable. Never mix oradd fuel to the fuel tank near any open flame.

6. Forbid inexperienced drivers to operate themachine. To acquaint a new driver with theoperation of the machine, reading this manualshould be a prerequisite.

7. Mentally prepare yourself for each race. Inthe event of an emergency, proper reactionsshould be somewhat automatic.

\J 4. Never use a match or cigarette lighter tocheck the fuel level. Do not smoke whilerefueling.

8. Keep feet, hands, and clothing away frommoving parts of the engine and drive train.Keep both feet on the running boards.

, . REGISTRATIONThe EXT carries absolutely no warranty either expressed or implied due to theabnormal usage of the machine.

To assist all EXT owners in the performance area of racing, Arctic Enterprises, Inc.will periodically send Racing News to all EXT owners; an Illustrated Parts Manual willalso be sent. To qualify for the factory racing news, the Arctic Cat EXT RegistrationCard must be completely filled out and sent to the factory for a mailing list. There-fore, at the time of sale, your dealer should complete the Registration Card and insureall information is correct. If you should change your address, please notify the factoryas soon as possible.

The engines are manufactured for optimum performance, and therefore, no modifica-tion is required.

Racing News will provide each owner with any factory modification, change in speci-fication and other items of general reference that will increase performance levels.If the factory modifies a component, the information will be sent to each registeredEXT owner, which will enable the modification to be performed correctly andefficientlv.

SUPPLEMENTAL PARTS INCLUDEDDescription 340 & 440 650

Quantity Quantity

Cylinder 2 3

Cylinder Gasket 2 3

Cylinder Head . 2 3

Cylinder Head Gasket 2 3

Piston Set wiRings 2 3

Piston Pin Set 2 3

Carburetor Gasket 2 3

Drive Belt 1 1

Spring (Orange) 1 1

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ARCTIC CAT 340 EXT SPECIFICATIONS

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ENGINE:Model ..Cylinders.DisplacementBoreStroke. . .Horsepower .Compression RatioPeak HP R.P.M.Piston ClearanceRing End Gap .TimingIgnition Type .Lighting Coil VoltagelWattageSpark PlugPlug Gap . . . .Carburetor . . .Fuel Mixture RatioCylinder Head Torque.Crankcase Torque . .Flywheel Torque. . .Maximum Engine Operating Temp..

DRIVE PULLEY:Model .Kawasaki Spring Tension. . .Arctic Spring Tension (Green)Engagement Speed . . . . .Drive Belt Width . . . . . .Outside Drive Belt Circumference

DRIVEN PULLEY:Model ...Spring Color

DRIVE/DRIVEN PULLEY:Center to Center DistanceOffset . . . . . . . . .

GEARING:With Arctic Drive PulleyWith Kawasaki Drive PulleyChain .

CHASSIS:Chassis MaterialBelly Pan MaterialHood Material .Length W/Skis .Height. . . .Overall Width .Track WidthTrack Length on Ground.Fuel Capacity . .Chaincase CapacityWeight. . . . . . . .

T7A340RX-12339 cc60mm60mm60 +7.5: 1 Effective95000.0045 Inch Max.0.006 - 0.012 InchTiming Mark on CrankcaseCD12 Volt/l00 WattNGK Bl0EV0.012 -0.016 InchMikuni VM-3620:116 Ft. Lbs.16 Ft. Lbs.60 Ft. Lbs.425 Degrees

Kawasaki & Arctic45 Lbs. Per Inch64 Lbs. Per Inch6500 R.P.M. With Gear Reduction1-1/4 Inch46-7/8 Inches (-!3/16 Inch)

CometRed

11-3/8 Inches.320 Inch

20T/35T39T/20T70 Pitch

AluminumFiberglassFiberglass94 Inches33 Inches33-1/2 Inches15 Inches30 Inches4-1/2 Gallons8 Ounces285 Pounds

ARCTIC CAT 440 EXT SPECIFICATIONSENGINE:Model ...Cylinders.DisplacementBoreStroke. . .Horsepower. . .Compression RatioPeak HP R.P.M.Piston ClearanceRing End Gap .TimingIgnition Type .Lighting Coil Voltage/WattageSpark PlugPlug Gap. . . .Carburetor . . .Fuel Mixture RatioCylinder Head Torque.Crankcase TorqueFlywheel Torque. . .Maximum Engine Operating Temp..

DRIVE PULLEY:Model .....Kawasaki Spring Tension.Arctic Spring TensionEngagement Speed . . .Drive Belt Width . . . .Outside Drive Belt Circumference

DRIVEN PULLEY:Model .Spring Color


GEARING:With Arctic Drive PulleyWith Kawasaki Drive Pulley.Chain .

CHASSIS:Chassis MaterialBelly Pan MaterialHood Material .Length WISkis .Height. . .Overall Width .Track WidthTrack Length on Ground.Fuel Capacity . .Chaincase CapacityWeight. . . . .

T7A440RX-l2436 cc68 mm60mm70 +7.5: 1 Effective8500 .0.0048 Inch Max.0.008 - 0.014 InchTiming Mark on CrankcaseCD12 Volt/l00 WattNGK Bl0EV0.012 - 0.016 InchMikuni VM-4020:116 Ft. Lbs.16 Ft. Lbs.60 Ft. Lbs.425 Degrees

Kawasaki & Arctic45 Lbs. Per Inch64 Lbs. Per Inch6500 R.P.M.With Gear Reduction1-1/4 Inch46-7/8 Inches (73/16 Inch)

CometRed




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ARCTIC CAT 650 EXT SPECIFICATIONS

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ENGINE:Model ..Cylinders.DisplacementBoreStroke. . .Horsepower .Compression RatioPeak HP R.P.M.Piston ClearanceRing End GapTimingIgnition TypeLighting Coil Voltage/WattageSpark Plug . . .Plug Gap .Carburetor . . . . .Fuel Mixture Ratio . .Cylinder Head Torque.Crankcase TorqueFlywheel Torque. . .Maximum Engine Operating Temp ..

DRIVE PULLEY:Model .....Kawasaki Spring Tension.Arctic Spring Tension . .Engagement Speed . . .Drive Belt Width . . . . . .Outside Drive Belt Circumference

DRIVEN PULLEY:Model ...Spring Color


GEARING:With Arctic Drive PulleyWith Kawasaki Drive PulleyChain .

CHASSIS:Chassis MaterialBelly Pan MaterialHood Material .Length W/Skis .Height. . . .Overall Width .Track WidthTrack Length on GroundFuel Capacity . .Chaincase CapacityWeight. . . . .

T8A650RX-13644 cc67.5 mm60mm100 +7.4:1 Effective8500 I

0.0048 Inch Max.0.008 - 0.014 InchTiming Mark on CrankcaseCD12 Volt/35 WattNGK B10EV0.012 - 0.016 InchMikuni VM-4020:116 Ft. Lbs.16 Ft. Lbs.60 Ft. Lbs.425 Degrees

Kawasaki & Arctic45 Lbs. Per Inch64 Lbs. Per Inch5500 R.P.M.1-1/4 Inch46-7/8 Inches Inch)

CometRed




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FUEL MIXINGThe correct engine lubricant and fuel mixture isvery critical to the performance of the Arctic Catengine.

A 100% synthetic lubricant developed especiallyfor racing is Arctic Cat Chemilube; it possesses nopetroleum oil whatsoever. Because of its superiorlubricating characteristics, the bearings, cylinders,pistons and rings are exceptionally well protected.Plug fouling and "load up" on the line are sub-stantially minimized.

Mixing Ratio

"WARNING"When mixing gas/oil or wheri filling the snow-mobile fuel tank, do not smoke.

The engine that powers the EXT snowmobile is ofthe two stroke principle, which requires the lubri-cating oil to be mixed with the gasoline for lubri-cating purposes and internal engine cooling.

The correct fuel mixture is five (5) gallons ofpremium gasoline (97 octane minimum) plus one(1) quart of Arctic Cat Chemilube.

II Note: The correct fuel mixture ratio is20:1. Mix twenty (20) parts of a good grade

premium gasoline (97 octane minimum) with one(1) part of two cycle air cooled engine oil (ArcticCat Chemilube). This is equivalent to one (1)quart of lubricant mixed with five (5) gallons ofgasoline (97 octane minimum).

e CAUTION eThe recommended fuel mixture ratio mustalways be strictly adhered to. Amixture con-taining an excessive amount of oil will causeextensive carbon formations on the piston,spark plugs, ports and in the exhaust system;resultants· are loss of power and pre-ignition.A fuel mixture containing too little oil willcause overheating; resultants may be pistonseizure and possible rod andbearing failure.

Mixing Procedure

II Note: Gasoline and oil will not mix well inextremely cold temperatures, therefore, it is

recommended that the oil be at room temperature(70°) when mixing.

1. Add 2-1/2 gallons of gasoline to a cleangasoline container.

2. Add the recommended amount of oil (1quart) and shake the mixture well.

3. Add an additional 2-1/2 gallons of gasolineand again, shake the mixture well.

When filling the EXT fuel tank, use a funnel witha fine mesh screen to prevent the entry of dirt orother foreign particles into the fuel system.

II Note: When using a gas/oil mixture that hasbeen setting for some time (settling of oil

may have occurred), shake the mixture beforefilling the fuel tank.

ADD 2% GALLONS ADD CHEMIl.UBE SHAKE MIXTURE ADD 2% GALLONSI

SHAKE MIXTURE

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PRE-OPERATING SAFETY CHECKS1. Check the cooling system. "Insure the cooling

fins are clean and free from obstructions.

2. Insure the exhaust system and carburetors aresecurely fastened.

3. Check the operation of the throttle control.The throttle control should depress withoutexcessive effort and return freely to the idleposition. Insure the emergency shut-offswitch is operating properly.

4. Check the brake control. The brake shouldfully engage when the brake lever is de-pressed approximately 3/4" and disengagefreely when released. If more than 3/4" ofbrake lever travel is necessary to engage thebrake, or if the brake lever bottoms on thehandle control, an adjustment is necessary.

5. Check the steering to insure the skis turnfreely. If difficulty is encountered in turningthe skis, remove ice or snow from around thesteering mechanism.

6. Check the machine fuel supply. Carry justenough fuel to complete a race, but alwayshave a minimum of one (1) gallon remain in

the tank after completion of race. Excessfuel will add weight, and consequently, retardthe performance of the machine during arace.

1. Insure that all nuts and bolts are properlytorqued. A. loose nut or bolt may causebodily injury' or serious damage to the ma-chine.

8. When the machine is operated in extremelycold weather or under slushy conditions, propthe back end of the machine up on a quick-jack and open the throttle slightly, allowingthe track to turn several revolutions. Thisrotation will allow the track to clear itself,and provide the bearings, track and drivebelt proper "warm-up" before subjectingthem to full load under race conditions.

.. WARNING"Do not allow anyone to stand to the front orto the rear of the machine or hold up the rearof the machine when either "warming up" or"clearing" the track.

BREAK-IN PROCEDUREStrict adherence to the following break-in proce-dure will contribute to the optimum life of theengine.

II Note: Do not alter the gas/oil mixture duringthe break-in period (5 operating hours).

For the first five (5) operating hours (approximate-ly one tank of fuel), the engine shou Id not be

subjected to heavy lugging or prolonged fullthrottle operation. During break-in, a maximumof three-fourths throttle is recommended. Varythe operating speeds but DO NOT subject the en-gine to constant speed operation for a prolongedtime.

After the break-in, check the entire machine forproper operation.

STARTING INSTRUCTIONSTO START:

..... WARNING .....Never allow anyone to stand in front of themachine when starting or when the engine isrunning.

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1. Insure all Pre-Operating Safety Checks havebeen satisfactorily carried out .

2. Position the emergency shut-off switch (A)in the ON position.

STARTING INSTRUCTIONS3. Make sure the tether pin (B) is inserted in the

tether switch.

4. Pull the starter plunger (e) on both carburet-ors fully upward. DO NOT HOLD THROT-TLE OPEN WHEN STARTING.

II Note: The engine will not start if the throttleis held slightly open when the starter plunger

is actuated (upward position). If the throttle isopened, the carburetors starting systems will bebypassed and an insufficient amount of fuel willnot allow the engine to start.

5. Grasp recoil starter handle (D) and pullslowly until recoil mechanism engages. Uponengagement, give a short, quick pull.

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7.

e CAUTION eTo avoid damaging the recoil starter mechan-ism, DO NOT pull the recoil rope to its limitor release rope from anextended position.

When the engine starts, immediately compressthe throttle and rev the engine to a fast idle(approximately 3000 RPM) for "warm-up".

Allow a cold engine to idle ("warm-up") forapproximately thirty (30) seconds beforeoperating the machine. Push both starterplungers fully downward after the "warm-up".

e CAUTION eIdling of a warm engine for more than thirty(30) seconds may cause excessive carbon for-mations, plug fouling and flooding. Placing acold engine under heavy load conditions (highRPM) may cause damage to the pistons andcylinders.

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AUXILIARY ROPE STARTINGIe Arctic Cat engine used in the EXT is equipped

with an auxiliary starting pulley, accessible byremoving the recoil starter should a failure occur.The starting rope IS located in the tool pouch; keepthe rope with the machine at all times.

MAINTENANCE AND ADJUSTMENTSCheck Before Each Race

Improper maintenance may lead to costly repairs,or a major breakdown. The following items shouldbe checked or serviced before each race: A) DriveBelt; B) Drive/Driven Pulley Offset; C) Drive/Driven Pulley Center to Center Distance; D) Track;E) Suspension; F) Brake; G) Electrical Connec-tions; H) Carburetion; I) Oil Level in Gear Reduc-" 'n Case and J) Proper Nut and Bolt Torque.

Carburetor, Throttle and Synchronization Adjust-ment

The engine used in the EXT employs Mikuni car-buretors for precise fuel/air mixture metering. TheMikuni carburetor is built with a fixed main jet,and therefore, no high speed adjustment is neces-sary. To insure optimum engine performance,both carburetors must be equally adjusted (SYN-CHRONIZED).

1. Open the hood.

2. Rotate the idle adjusting screws (A) counter-clockwise until the idle adjusting screw tipis flush with the side of the carburetor bore.

3. Loosen the jam nuts (B) on both throttlecables and rotate the swivel adapter until thethrottle slide fu Ily seats in the recess of thecarburetor bore. Lock the jam nuts andswivel adapter into position.

Rotate both idle adjusting screws (A) clock-wise until the screws contact the throttleslide. At that instant, the throttle slide willbegin to rise.

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5. Rotate the idle adjusting screws (A) an addi-tional two (2) turns clockwise.

6. Loosen the jam nuts (B) on both throttlecables and rotate the swivel adapter counter-clockwise until all slack has been removedfrom the throttle cable. Lock the jam nutsand swivel adapter into position.

7. Look into the throat of all carburetorsand slowly compress the handlebar-mountedthrottle lever. All throttle slides must beginto rise at precisely the same instant. Ifthrottle slide movement does not occur asspecified, repeat steps 2 - 6.

8. Carefully rotate both pilot air screws (C)clockwise until a slight seating resistance isfelt.

9. Rotate both pilot air screws (C) one (1)revolution counterclockwise.

MAINTENANCE AND ADJUSTMENTS10. The idle speed may not be suitable for normal

operation, even though the carburetors aresynchronized. To check the engine forproper idle, proceed as follows:

A. Run the engine until normal engineoperating temperature is achieved.

B. If the engine will not idle or if a higheridle RPM is desired, rotate the idleadjusting screws (A) clockwise until thedesired idle is obtained.

II Note: Set both idle adjusting screws (A)equally. If the idle adjusting screws are not

adjusted equally, it will be necessary to repeatsteps 2·8.

11. Close the hood.

Carburetion (Fine Tuning)

1. CHECK FLOAT LEVE L '- The fuel level inthe float chamber is governed by the projec-tion of the two float arms. If there is dirtbetween the needle valve and seat preventingthe valve from closing, if there is wear ordamage in the needle valve area or if thefloatts) is punctured, fuel overflow mayoccur. Conversely, if the needle sticks to theseat, a very limited amount of fuel will flowinto the float chamber.

A. Remove the float chamber body andgasket from the main body of the car-buretor and invert the carburetor.

B. Measure the distance (0) from the gas-ket surface to the top edge of the floatarm. For the Mikuni VM-36 carburetor,the distance should be .693 inch or17.8mm: for a VM-40 carburetor, thedistance should be .693 inch or 17.8mm.When an adjustment of the float arm isnecessary, bend only the float armactuating tab.

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2. SELECT MAl N JET - Main jets for the EXTwill have an approximate graduated rangefrom 370 to 390. In this graduated range,main jet sizes are increased in steps of ten:370, 380 and 390. The larger the number,the greater diameter of the jet orifice and asa result, a richer fuel/air mixture.

A. Run the machine on a flat hard-packedarea at full throttle. If the engine drags,or labors at full throttle, the main jetorifice (size) is too large. To remedy,install the next smaller size jet and re-peat full throttle operation on a flathard-packed area. Continue changingjets until the engine runs efficiently atfull throttle as explained previously.Check the condition of the spark plug(see Spark Plug, page 22).

B. If the engine runs efficiently at fullthrottle to begin with, the jet shouldstill be checked for proper size; the jetmay be contributing to a lean condition.If this condition does exist, install amain jet which is two sizes larger. Runthe machine on a flat hard-packed area;when the engine drags, use the nextlower sized main jet. Engine should nowoperate efficiently. Check the conditionof the spark plug (see Spark Plug, page22).

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MAINTENANCE AND ADJUSTMENTSF. Shut the engine off.

H. The pilot air screw adjustment shouldrange from 1 to 2-1/2 turns out fromthe full seated position.

J. The engine may idle smoothly withoutthe pilot air screw in the 1 to 2-1/2 turnrange but smooth acceleration will notbe evident during mid-range operation.

If it takes 1 turn or less, the pilot jetis too small and must be replaced by alarger pilot jet. If it takes 2-1/2 turns ormore, the pilot jet is too large and mustbe replaced by a smaller pilot jet.

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G. When the desired idle speed has beenattained, cautiously rotate the pilot airscrew in andat the same time, count thenumber of turns required to seat thescrew..

e CAUTION eDO NOT force the pilot air screw; doing somay cause damage to the screw or seat.

II Note: Pilot jets will have an approximategraduated range from 30 to 35. In this

graduated range, pilot jet sizes are increased insteps of five: 25, 30 and 35. The larger thenumber, the greater diameter of the jet orifice andas a result, a richer fuel/air mixture.

D. Rotate the pilot air screw (A) in or outuntil the engine runs smoothly.

A. Prop the back end of the machine up ona Quick Jac and start the engine.

C. Slowly back the idle speed adjustingscrew (8) out until the engine begins todie out.

8. Slowly rotate the idle speed adjustingscrew (8) in until the engine begins toidIe faster.

3. ADJUST PI LOT AI R SCR EW (A) - Throttleslide must be resting against the idle speedadjusting screw before any adjustment isinitiated. Observe this condition by lookinginto the bore of the carburetor.

II Note: Rotating the pilot air screw in willrichen the fuel/air mixture and rotating out

will lean the fuel/air mixture.

E. Perform steps C, D and E until theproper engine idle speed is attained.

4. THROTTLE SLIDE CUT - AWAY - Theamount of throttle slide cut-away affects thefuel/air mixture from 0 to 1/4 throttle slidemovement. Throttle slides are stamped witha number (1.5, 2.0, 2.5, 3.0, 3.5, etc.): thesenumbers reflect the degree of cut-away. Thelarger the number, the greater portion ofthrottle slide cut-away, which results in aleaner initial fuel-air mixture.

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MAINTENANCE AND ADJUSTMENTS

A. Start the engine. From an idle, acceler-ate to 1/4 throttle. If the engine hesi-tates or if "spit back" occurs, a leancondition exists (throttle slide cut-awaytoo large).

B. Conversely, if the engine drags or four-cycles while accelerating to 1/4 throttle,a rich condition exists (throttle slide cut-away too small). When this conditionexists, rotate the pilot air screw 1 turn(maximum) out. If this adjustment doesnot correct the condition, the nextlarger numbered throttle slide should beinstalled.

5. NEEDLE SELECTION - The needle can beset in one of five different positions bymoving the needle clip to a different groove.For fine tuning purposes, number the groovesfrom 1 - 5, starting from the top groovedown. The number 1 groove gives the leanestsetting, whereas the number 5 groove givesthe richest setting.

The needle is stamped with a number andletter series for a certain specific measure-ment such as4G L3.

A. FI RST NUMBER - Designates the totallength of the needle. The larger thenumber, the longer the needle. The fourstands for 40mm long but not to exceed50mm.

B. LETTERS - The amount of taper anddegree of richness is depicted by thetwo letters. The needle is tapered ingraduated steps. The first letter indi-cates the upper taper angle and thesecond letter indicates the lower taperangle. As an example, the letter "A"equals 0015'; each successive letter is agreater angle by 15'. "G"=1 045' and"L"=3000' .

A "G" needle will have more taper thanan "F" needle, and therefore provides aricher fuel/air mixture through mid-range operation.

C. SECOND NUMBER - Indicates themanufacturer lot number and will varywith different needles.

6. NEED LE JET - The needle jet comes invarious sizes and works in direct relation withthe needle. The needle jet orifice diameterremains constant through the entire length ofthe jet, and therefore, changing the needle jetwill have a greater affect on mid-range oper-ation than a groove change on the needle.

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MAINTENANCE AND ADJUSTMENTSThe needle jets have a stamped letter fol-lowed by a number, such as N3 or 02. Eachletter is graduated in increments of ten digits.i.e. NO, N1, N2, N3, N4, N5, N6, N7, N8,N9, 00, 01,02,03 and 04 etc.

A. LETTER - Designates the orifice size,which means that an "0" needle jetprovides a richer fuel/air mixture thana "N" needle jet.

B. NUMBER - Relates the specific dia-meter of the needle jet. For example,N2 means the inside diameter of theneedle jet is 2.560mm.

7. MID-RANGE TUNING - Fine tuning themid-range is similar to tuning the main jet.For example, use a rich needle position anda rich needle jet until four-cycling is evident.When the four-cycling affect exists, installthe next leaner needle or needle jet to assurethe proper fuel/air mixture is obtained.

II Note: All the adjustments mentioned pre-viously will overlap into the next graduated

range, which is necessary to provide smoothacceleration. A main jet change will affect themid-range operation by approximately 10%. If aone groove needle change is made, it will affect themain jet by approximately 10%.

o 2 3 9

N 2.550 2.555 2.560 2.565 2.595

o 2.600 2.605 2.610 2.615 2.645

P 2.650 2.655 2.660 2.665 2.695

CARBURETOR SPECIFICATIONS

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Engine Model1. Carburetor Type2. Main Jet3. Air Jet4. Jet Needle5. Needle Jet6. Slide7. Pilot Jet8. Bypass Hole9. Pilot Outlet10. Air Screw11. Inlet Seat12. Starter Jet13. Fuel Level14. Bypass Pitch15. Pump

(Factory Equipped)

340VM363802.06DH4-30-52.0351.40.61.01.51.533.03.8DF52

440VM40380

7DH2-3AA-51.5301.40.81.01.51.537.04.5DF52

650VM40380

7DH2-3AA-51.5301.40.81.01.51.537.04.5DF52

Lubrication

The oil bath chaincase, gear reduction case, drivenpulley and rear suspension arms must be properlylubricated to insure efficient operation.

... WARNING'"Engine must not be runningwhen performingthe following maintenance on the machine.

1. Oil Bath Chaincase - The lubricating oilshould be checked at the check plug (A)before every day of racing. The lubricantlevel should be at the point of overflowing inthe check plug hole. If lubricant is low, addArctic Chainlube through the filler hole(B). When lubricant is at the point of over-flowing in the check plug hole (A), installboth plugs.

II Note: If oil deposits are observed in thebelly pan, check the chaincase gasket for

deterioration. If chaincase gasket is suitable, checkthe sealing capacity of the driven shaft bearing and"0" ring. Replace components as conditionsdictate.

2. Gear Reduction Case - The lubricant in thegear reduction case should be checked at thefiller plug (C) prior to every day of racing.The lubricant level should be at the point ofoverflowing in the filler plug hole. If thelubricant is low, add Hypoid No. 90 lowtemperature lubricant. The lubricant in thegear reduction case should be changed afterevery five (5) operating hours. A drain plugis located at the bottom of the gear reductioncase for drainage purposes.

3. Driven Pulley - Lubricate the driven pulleyassembly each month by using the followingprocedure.

A. Remove the drive belt (see Drive Belt,To Remove, page 19).

B. Open the pulley by pushing and rotatingthe movable face toward the inside ofthe machine.

II Note: It will be necessary to insert an objectbetween the fixed and movable face to insure

the faces remain open.

C. Apply a thin coat of low-temperaturegrease (Texaco 2346EP or equivalent)on the pulley hub (0). Work themovable face open and closed severaltimes to distribute the lubricant overthe entire pulley hub. Lubricate thebearing fitting (E) with the same low-temperature grease.

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MAINTENANCE AND ADJUSTMENTSD. Using a clean rag, wipe off any excess

lubricant from the hub, fixed face,movable face, and the grease fitting.

II Note: Excessive lubricant on the pulley hubwill be thrown onto the drive belt by centrif-

ugal force, causing belt slippage and deterioration.

E. Replace the drive belt (see Drive Belt,To Install, page 19).

4. Rear Suspension Arms - Lubricate the rearsuspension arms (A) before each day of racingwith low-temperature grease (Texaco 2346EPor equivalent).

II Note: Due to the position of the suspensionarm grease fitting it is recommended that a

flexible hose grease gun be used for this lubri-cating purpose.

Brake

The brake used on the 1973 EXT is a non-assisteddisc brake mounted on the driven shaft, which isactuated by compressing the lever mounted on theleft handlegrip. This brake provides excellentbraking capabilities for the machine during racingsituations. Prior to each day of racing, the brakeshould be checked. The brake is properly adjustedwhen the brake lever has approximately 3/4 inchfree travel from the end of the lever to the handle-grip.

TO ADJUST:

1. Remove the cotter pin (8).

2. Rotate the locknut (e) until proper adjust-ment is obtained.

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Drive Pulley (Arctic)

The drive pulley is a torque sensing, RPM typedrive mechanism designed to transfer peak horse-power from the engine to the track. The springand weights inside the drive pulley react with eachother to overcome the centrifugal force applied toit by the engine RPM's. The primary function ofthe spring is to resist the force of the weights forengagement purposes.

Operating Characteristics

1. If the weights are too light the drive pulleywill generally engage fairly well ... Imme-diate high RPM will be obtained but the beltwi II not ride to the top of the pu lIey, andtherefore, optimum power transfer will notbe accomplished soon enough. A flat spotduring acceleration will be evident.

2. If the weights are too heavy, the drive pulleywill engage properly but a high ratio will beobtained because the engine RPM's are low.The RPM's will gradually increase to peakpower transfer. The condition will be evidentby a flat spot during acceleration.

3. When the weights and springs are properlymatched, the drive pulley will engage proper-ly and accelerate smoothly. Top speedshould be reached at the end of an oval track,whereupon deceleration occurs resulting in alower drive ratio. After the corner has beennegotiated, smooth acceleration again shouldtake place until the end of the next straight-away.

MAINTENANCE AND ADJUSTMENTSDriven Pulley

The driven pulley is relatively maintenance free.The driven pulley should be visually inspectedeach week for damage, cracks and belt build-upon the ·driven pulley hub. The driven pulley isadjustable by means of a tension spring attachedto a movable plate. Increasing the spring tensionwill retard shifting to a higher ratio. Decreasingthe spring tension will facilitate shifting into ahigher ratio.

TO ADJUST:

1. Place the end of a snug fitting punch in oneof the movable plate holes.

2. While exerting pressure on the punch, placea screwdriver behind the movable plate andcarefully pry it toward the driven pulley untilthe plate becomes disengaged. Keep movableplate in the disengaged position.

Drive/Driven Pulley Offset

To assure optimum power transfer, the offset mustbe .320 inch. The offset is changed by moving theflatwashers located to the inside of the drivenpulley movable face.

II Note: If a f1atwasher is removed from theinside of the driven pulley, it must be in-

stalled on the outside (fixed face) of the drivenpulley. This procedure must be followed to main-tain proper driven shaft end-play.

!\'COC' ,

1. Remove the capscrew and flatwasher(s) thatsecure the driven pulley to the driven shaft.

2. Move the required number of flatwashers tothe proper end of the driven pulley to obtainthe recommended offset (.320 inch).

3. Secure the driven pulley to the driven shaftwith the capscrew and flatwasher(s).

II Note: Check the offset before each day ofracing or when a new drive belt is installed.

e CAUTION eConstant pressure must be exerted on thepunch to prevent a sudden uncoiling of thespring. Failure to comply may cause damageto variouscomponents.

3. By exerting pressure on the punch, rotate themovable plate clockwise to increase springtension. Rotate counterclockwise to decreasespring tension.

4. Slowly remove the screwdriver and allow themovable plate to securely seat itself. Releasepressure on the punch.

Drive/Driven Pulley Center Distance

The correct center to center distance between thedrive and driven pulley is 11-3/8 inches. Themeasurement should be taken from the center ofthe drive pulley bolt to the center of the drivenpulley bolt. The motor plate is slotted to accurate-ly obtain the specified center to center distance.

17

MAINTENANCE AND ADJUSTMENTSTO ADJUST:

1. Loosen the nuts securing the engine andengine plate to the rubber engine mounts.

2. Slide the engine and engine plate in theproper direction to obtain the specified cen-ter to center distance (11-3/8 inches).

II Note: When the adjustment is being per-formed, always keep the crankshaft parallel

with the driven shaft. Doing so will insure properalignment.

3. Secure the engine and engine plate in positionby tightening the engine mount nuts.

II Note: Check the center to center distancebefore each day of racing or when a new drive

belt is installed.

Drive Chain

The drive chain must always be immersed in oil toprovide proper lubricating qualities; check thiscondition before each day of racing. The oil levelin the oil bath chaincase must always be at thepoint of overflowing in the check plug hole (seeLubrication, Oil Bath Chaincase, page 15). Toeliminate constant adjustments the drive chain iscontrolled by an automatic chain tensioner.

TO CHECK CHAIN TENSION:

Check the drive chain tension prior to each day ofracing.

1. Rotate the brake disc toward the rear of themachine until all free play has been removed.

2. Mark the top surface of the brake discdirectly below the center of the brake bracketcasting mount.

3. Rotate the brake disc forward until the freeplay has been eliminated.

4. Distance (A) from the mark on the top sur-face of the brake disc to the brake bracketcasting mount should be from 1/8 to 1/4inch.

5. If tension is not as specified, see To AdjustChain Tension, page 18.

18

i

/'-. -- _....... " ..

TO ADJUST CHAIN TENSION:

Proper chain tension is conducive to both chainand sprocket durability. If the drive chain rattlesin the chaincase, if chain slippage is evident or ifabnormal vibration occurs, an inspection of thedrive chain tensioners is necessary.

1. Place rags in the belly pan, just below thechaincase.

2. Remove the capscrews and star washers secur-ing the chaincase cover to the chaincase. Re-move the chaincase cover and allow thechaincase lubricant to flow into the rags inthe belly pan.

II Note: Do not damage the chaincase gasketwhen removing the chaincase cover.

3. Examine the chain tensioner shoes and springfor wear, deterioration and breakage. Re-place these components as conditions dictate.

II Note: Insure a good seal is obtained betweenthe chaincase cover, gasket and chain case.

5. Remove the chaincase filler plug and thecheck plug. Slowly pour Arctic Chainlubethrough the upper filler hole until the level isat the point of overflowing in the check plughole.

......-e-,,,,- . 4.

MAINTENANCE AND ADJUSTMENTSInstall the chaincase cover to the chaincaseand secure in place with the capscrews andstar washers.

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6. Replace the check plug and the filler plug.

Drive Belt

Before each race or heat examine the conditionof the drive belt. The drive belt should always bein excellent condition. The drive belt width is1-1/4 inch as supplied from the factory. The out-side circumference of the drive belt should mea-sure 46-7/8 inches with a tolerance of inch.When the width has decreased to approximately1-1/8 inch, if the belt has stretched, if otherwisedamaged or if slippage occurs, the drive beltshould be replaced.

II Note: To insure optimum power transfer,drive belt must be kept free of dirt, oil,

grease, gasoline and moisture, whether being usedor while in storage.

TO REMOVE:

1. Open the hood.

2. Disengage the pulley guard and pivot theguard toward the front of the machine toprovide access to the drive/driven pulley andthe drive belt.

3. Rotate and pull the movable face of thedriven pulley toward the inside of the ma-chine. Grasp the drive belt, pull upward androtate the drive belt over the top of thedriven pulley fixed face. Carefully releasethe movable face.

4. When the drive belt is free of the drivenpulley, slide the drive belt off the drivepulley.

TO INSTALL:

1. Position the drive belt in the drive pulley.

2. Rotate and pull the movable face of thedriven pulley toward the inside of the ma-chine. Grasp the drive belt and position iton the bottom surface of the driven pulleyfixed face. Pull the drive belt to the insideof the driven pulley and continue to rotatethe belt forward and over the fixed face.

3. Slowly release the fixed face.

Suspension

The machine is equipped with a slide rail typesuspension system. The suspension should beadjusted for the weight of the operator and thecondition of the racing track surface. Alwaysadjust the front and rear spring to cope withexisting conditions. The front and rear springsserve two distinct purposes and possess certainoperating characteristics when adjusted different-ly. Rear Springs - should be adjusted to support

19

MAINTENANCE AND ADJUSTMENTSthe rider without bottoming but soft enough togive a good ride. Front Springs - should beadjusted for the racing track conditions (hard-packor soft snow). Hard Pack Track Condition - Theadjusting bolts should be tightened to maintainmaximum machine track surface on the racingtrack. Soft Snow Track Condition - The adjustingbolts should be loosened to allow the track topropel itself and remain on top of the snow.

II Note: Always adjust the front and rearadjusting bolts equally.

Track Tension

Proper track tension is essential to winning races.If the track is too loose it could possibly scrapethe inside top of the body tunnel causing damageto both the chassis and cleated track. If the trackis too tight, increased pressure will be exerted onthe slide rail hi-fax strips, resulting in a substantialperformance loss. Desired distance between thetrack and the bottom of the slide rail should befrom 1 - 1-1/4 inch at mid-span.

-__ __m_

ai;aar;;B-id20

TO ADJUST:

1. Support the rear of the machine off theground and make sure the entire track is freeto turn.

2. Measure the distance between the track andthe bottom of the slide rail.

3. Rotate track tension adjusting bolts clockwiseto tighten the track tension and counterclock-wise to relax the track tension.

4. Whenever the track tension is adjusted thetrack alignment must be checked (see TrackAlignment, page 20). Track tension andtrack alignment adjustment have a directaffect on each other.

Track Alignment

The track is a molded full-length aluminum cleatdesign. The total weight is considerably lowerwith this type of track. Track alignment should bechecked prior to each race. The track should becentered between the sides of the body tunnel.

!I

MAINTENANCE AND ADJUSTMENTSTO ADJUST:

1. Support the rear of the machine with a QuikJac and insure the entire track is off theground and free to turn.

2. Loosen the locknuts on both ends of the tierods.

3. Pull both ski tips outward and rotate the tierods until a parallel alignment is obtained.

2. Start the engine, accelerate slightly to turnthe track several revolutions and SHUT EN-GINE OFF. Allow the track to stop rotatingby itself; do not actuate the brake.

3. Note whether the track has moved to eitherside.

4. If the track runs to the left or right, tightenthe appropriate track tension bolt until thetrack is centered between the rear of thebody tunnel.

r--.::---- --" ---''\' . _.- .. -- ----. --, . - -.'-:.

" \: -------- -c,,\:. M)'>--7 )I ",I> /;'<: u_._

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4. Secure the locknuts in place

Fuel Filter

::::::::..:::::"

::::::::::--::;::;

5. Whenever the track alignment is adjusted, thetrack tension must be checked (see TrackTension, page 20). Track alignment andtrack tension adjustment have a direct effecton each other.

Ski Alignment

The machine is equipped with carbide skags whichenhance the high speed handling characteristicsthat are necessary during a race. Proper alignmentof the skis is essential to winning a race and alsofor the safety of the operator. Proper ski-align-ment is when the skis are PARALLE L. Absolutelyno "toe-in" or "toe-out" should be evident.

TO ADJUST SKIS:

1. Measure the distance between the skis at thefront and rear spring mounts. .

The 1973 EXT snowmobile is equipped with abrass screen fuel filter located inside the fuel tank.To examine the condition of the fuel filter, pro-ceed as follows:

1. Form a hook on the end of a piece of stiffwire.

2. Remove the gas cap, insert hook through thefiller hole, and hook the gas tank hose.

3. Carefully pull the hose and filter assembly upthrough the filler hole.

4. If filter is dirty, remove it from the hose andwash in a container of clean gasoline. Installfilter.

_ Note: Do not clean fuel filter by scraping_ with a wire brush or similar tool, as this may

21

MAINTENANCE AND ADJUSTMENTSdamage the screen, allowing foreign particles toenter the gas line. Always replace a damaged fuelfilter.

Spark Plug

Heat Range - In some cases it may be necessaryto change the heat range when using specific plugs.For recommended spark plug type, see EngineSpecifications, pages 4, 5 and 6.

A cracked, fouled or dirty plug should be replaced.DO NOT clean and re-use old spark plugs; grit maybe released into the cylinder, causing severedamage.

Tan or Light Brown Insulator Tip - Indicatescorrect type, proper heat range, and correct car-buretor setting.

22

Light Gray or White Insulator Tip - Indicatesoverheating caused by a lean carburetor setting,overloading, or incorrect (hot) spark plug. If thecarburetor is properly adjusted, replace the plugwith one of a colder heat range.

Black Insulator Tip - Indicates fouling caused byexcessive oil, a rich carburetor setting, or incorrect(cold) spark plug. If gas/oil mixture and car-buretor adjustment is correct, replace spark plugwith one of a hotter heat range.

Gap Setting - The spark plug gap should be setat .012 - .016".

II Note: When heat gauge sending units areinstalled, spark plug gaskets must be removed.

If sending units are removed, the spark plug gas-kets must be installed.

TROUBLE SHOOTINGJ Problem Condition Cause

Engine Fails to Start (Weak or No Spark) Emergency Switch OFFIgnition Switch OFFWet or Fouled Plug(s)Incorrect Spark Plug GapFaulty WiringFaulty Ignition SwitchFaulty Ignition Coil(s)

Engine Fails to Start (Incorrect Fuel/Air Mixture) Throttle Lever OpenedCarburetor MisadjustedFaulty CarburetorIntake Manifold Leaking Air

Engine Fails to Start (No Fuel) Fuel Tank EmptyFuel Line DisconnectedFuel Line Pinched or KinkedFuel Filter DirtyImpulse Line DisconnectedImpulse Line KinkedGasCap Vent Hole Obstructed

Engine Fails to Start (Poor Compression) Cylinder Head LooseSpark Plug(s) Loose"Blown" Head GasketRing(s), Pistonts), or Cylinder(s) Damaged

Running Failure (Engine Lacks Power) Carburetor MisadjustedFaulty CarburetorAir Leak Around CarburetorPoor CompressionImproper Ignition TimingExhaust Port Plugged

Running Failure (Engine Backfires) Carburetor MisadjustedFaulty CarburetorIncorrect Spark Plug(s)Air Leaks at CarburetorIncorrect Ignition Timing

Running Failure (Engine "Four-Cycles") Carburetor MisadjustedFaulty CarburetorExhaust Port Plugged

Running Failure (Engine Pings [Detonation]) Incorrect Spark Plug(s)Carburetor MisadjustedImproper Ignition TimingExcessiveCarbon on Head(s) or Piston(s)Poor Grade of Gasoline

Running Failure (Engine Idles Poorly) Carburetor MisadjustedFaulty CarburetorFaulty Spark Pluqls)Incorrect Spark Plug(s)

I Incorrect Ignition Timing

23

EXT IDENTIFICATIONThe 1973 EXT snowmobile has three identifyingnumbers. Please make a record of them and keepit in a safe place.

The chassis model and serial number plate islocated on the right side of the body tunnel justbelow the gas tank. All records are kept numeri-cally by the chassis serial number.

The body serial number is stamped into the bodytunnel just below the chassis serial number plate.It is important because it can be used to identifyyour machine in case of theft.

The engine model is located on the engine nameplate and the serial number is stamped in themagneto cover.

Always provide the snowmobile name, enginemodel, and serial numbers when contacting yourauthorized Arctic Cat dealer concerning parts orservice.

.' .'

MAINTENANCE LOGHours Lubri- Chain Gear Suspension Driven Drive Center Carbu- SparkDate Offset to TrackUsed cation Case Reduction Arms Pulley Pulley Center retor Plug

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arctic cat 1973 owners manual

Documents

drive pulley

factory racing news

ext owners

ext identification

registrationthe ext

fuel tank

fuel level

fuel filter