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6.2 CYLINDER AND PISTON REMOVAL

 

 

Remove the seat and rear fender. 
Remove the exhaust pipe. 
Remove the spark plug cap. 
Disconnect the wire.

 

Drag out the engine.

 

Disassembly the air cleaner and carburetor.

 

 

 

 

 

 

 

 

 

 

Remove the intake pipe mounting bolts.

 

Remove the cylinder bolt nuts.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Remove the cylinder head.

 

Remove the cylinder carefully, then you can see 
the whole piston.

 

Remove one piston pin clip. 
Remove the piston and piston pin.

 

Spread each piston ring and remove it by lifting up

 

at a point just opposite the gap.

 

Note: Don’t let the clip drop into engine crankcase.

 

 

 

 

 

 

 

 

 

6.3 CYLINDER AND PISTON INSPECTION

 

 

Inspect the cylinder bore for wear or damage. 
Measure the cylinder inner diameter at three levels 
in X and Y-axis.

 

Taper limit: 0.10 mm

 

Out of round: 0.10 mm

 

Summary of Contents for VIPER 50 ST - SERVICE

Page 1: ...SERVICE MANUAL...

Page 2: ...ND INSTALLATION 4 ENGINE FUEL SYSTEM 5 ENGINE LUBRICATION AND COOLING SYSTEM 6 ENGINE COMBUSTION SYSTEM 7 TRANSMISSION SYSTEM 8 STEERING SYSTEM 9 FRONT WHEEL SYSTEM 10 REAR WHEEL SYSTEM 11 FENDERS AND...

Page 3: ...ctor if electrolyte gets in your eyes HOT PARTS Engine and exhaust pipe become very hot and remain hot for one hour after the engine is run Wear insulated gloves before handling these parts USED ENGIN...

Page 4: ...nST EXL 50 CHASSIS Overall Length 1670 mm 1750 mm Overall Width 940 mm 1010 mm Overall Height 1040 mm 1065 mm Seat Height 760 mm 760 mm Wheel base 1110 mm 1115 mm Ground Clearance 120 mm 120 mm Dry We...

Page 5: ...perST EXL 50 YukonST EXL 50 in this service manual The frame serial number is stamped on the front of the frame The engine serial number is stamped on the left side of the crankcase Frame serial numbe...

Page 6: ...ft Steering shaft nut 50 N m 36 9 lbf ft Steering shaft holder bolt 33 N m 24 lbf ft Wheel rim bolt 18 N m 13 3 lbf ft Tie rod lock nut 35 N m 25 8 lbf ft King pin nut 40 N m 29 lbf ft Handlebar lowe...

Page 7: ...PLUG 25 30 N m TIE ROD LOCK NUT 35 43 N m ENGINE OIL JASO FC Grade or same degree oil GEAR LUBRICATION OIL SAE 90 2 2 MAINTENANCE SCHEDULE The maintenance internals in the follow table is based upon...

Page 8: ...ottle cable replace it if necessary Check the throttle lever free play is 5 10 mm at the tip of the throttle lever Disconnect the throttle cable at the upper end Lubricate the cable with commercially...

Page 9: ...e a new spark plug if the electrodes and insulator tip appear unusually fouled or burned Discard the spark plug if there is apparent wear or if the insulator is cracked or chipped The spark plug gap s...

Page 10: ...e drive chain with kerosene and wipe it dry Inspect the drive chain for possible wear or damage Replace the chain if it is worn excessively or damaged Inspect the sprocket teeth if it is excessive wea...

Page 11: ...ess Service Limit 2 0mm 0 08 inch If either lining is worn beyond the service limit replace Both brakes shoes 2 11 WHEELS AND TIRES Inspect the tire surfaces for cuts nails or other sharp objects Chec...

Page 12: ...ground and the front wheels facing straight ahead Mark the centers of the tires to indicate the axle center height Measure the distance between the marks Carefully move the vehicle back let the wheels...

Page 13: ...Gear oil needs to be changed every year There is a gear oil release bolt at the rear of engine Unscrew this release bolt and can let the dirty oil flow out The re add oil hole is on the engine case b...

Page 14: ...the exhaust pipe Disconnect the carburetor cable by unscrew two screws on top of the carburetor Take off oil pump cable from the oil pump control plate Oil pump is under the right side of engine Disco...

Page 15: ...3 3 ENGINE INSTALLATION Engine installation is essentially the reverse order of removal The torque of engine hanger bolt is 24 30 Nm Route the wires and cable in reverse order properly...

Page 16: ...KS FUEL TANK CAP BREATHING HOLE CLOGGED LEAN MIXTURE FUEL JET OF CARBURETOR CLOGGED FUEL TANK CAP BREATHING HOLE CLOGGED FUEL FILTER CLOGGED FUEL FLOWS IN THE TUBE UNSMOOTHLY FLOAT LEVEL IN CARBURETOR...

Page 17: ...leaner Disconnect the fuel line and auto choke electric wire Unscrew the intake pipe mounting bolts at the carburetor then removes the carburetor Note Turn fuel cup on off position Remove the carburet...

Page 18: ...ect the seat of the float needle valve for wear or damage Disassembly the slow jet main jet throttle adjusting screw and air flow adjusts screw Inspect all the jets and screws for wear or damage Clean...

Page 19: ...order of disassembly THROTTLE VALVE ASSEMBLY Install the needle clip on the jet needle Install the jet needle into the throttle valve Assembly the throttle cable spring and the throttle valve Align t...

Page 20: ...uantity is not enough this engine will be serious scratched and then this engine will stop even cannot work again When this engine is serious scratched you need to change the piston piston rings and c...

Page 21: ...IN OIL TANK IS TOO LOW OIL TUBES WERE NOT FIXED WELL OIL HAS LEAKAGED FROM TUBE ENDS OIL TUBES WERE BROKEN OIL TUBES WERE CLOGGED OIL PUMP CANNOT WORK ALWAYS INSUFFICIENT OIL LEVEL EXTERNAL OIL LEAKS...

Page 22: ...S WORN OUT HIGH COMPRESSION EXCESSSIVE CARBON BUILD UP ON PISTON HEAD OR IN COMBUSTION CHAMBER EXCESSIVE NOISE PISTON AND CYLINDER WORN OUT EXCESSIVE CARBON BUILD UP EXCESS SMOKE CYLINDER OR PISTON RI...

Page 23: ...ve the cylinder head Remove the cylinder carefully then you can see the whole piston Remove one piston pin clip Remove the piston and piston pin Spread each piston ring and remove it by lifting up at...

Page 24: ...r gauge Service limit 0 10 mm Insert each piston ring into the cylinder and measure the end gap Service limit 0 5 mm Measure the clearance between ring and groove Service limit 0 09 mm Measure the pis...

Page 25: ...Measure the connecting rod small end inner diameter with a small bore diameter gauge Service limit 14 06 mm 6 4 INSTALLATION Install the piston rings with the marks facing up Do not damage the piston...

Page 26: ...exhaust pipe Do not align the piston pin clip end gap with the piston cutout Install a new cylinder gasket Apply a thin coat of engine oil to the piston rings and cylinder wall Install the cylinder co...

Page 27: ...SYSTEM 7 1 TROUBLESHOOTING ABNORMALLY ACT IN SHIFTING AND CAN T RESET FAULTY C D I FAULTY SHIFT MOTOR FAULTY SENSOR F N1 R N2 FAULTY SHIFT SPRING OR GEAR CAN NOT MOVE AFTER ENGINE START BELT WORN FRO...

Page 28: ...Shift Mechanism Gear Box For...

Page 29: ...h loctite 5699 and screw with torque 25 kgf cm in assembly SERVICE LIMITS 30 mm TORQUE 25 kgf cm Shift Spring and Gear Remove mission side cover and other parts Check shift gear for wear or damage Mea...

Page 30: ...belt by the centrifugal force from six rollers Then the pitch circle of belt in drive pulley will be larger The belt at driven pulley is forced to move to the center of shaft then the radius of pitch...

Page 31: ...ate to increase to high torque toward to low speed and make the engine maintain smooth running with original revolution 7 6 GEAR BOX Reverse Shaft Comp Sensor Drive Shaft Comp Drum Gear Shift Fork For...

Page 32: ...the engine is started the kick started will stop transfer the power to the kick starter driven gear When the kick starter lever is released the kick starter gear will go back to its original position...

Page 33: ...FRONT WHEEL WOBBLING STEERS TO ONE SIDE Faulty tire Steering shaft holder too tight Insufficient tire pressure Faulty steering shaft bushing Damaged steering shaft bushing Faulty tire Worn front brak...

Page 34: ...bsorber swing rod SOFT SUSPENSION Weak front shock absorber springs Worn or damage front swing arm bushings 8 3 HANDLEBAR REMOVAL Remove the right side handlebar cover by unscrew two fix screws Remove...

Page 35: ...ower holders Install the handlebar upper holders with the L or R marks facing forward Tighten the forward bolts first and then tighten the rear bolts Install the handlebar upper holder s cover Install...

Page 36: ...cover and gasket Disconnect throttle cable from the throttle arm and remove from the throttle housing Assembly is in the reverse order of disassembly 8 5 STEERING SYSTEM Removal of Kingpin and Tie ro...

Page 37: ...r cover and handle bar See paragraph 8 3 Remove the front fender See paragraph 10 1 Remove handlebar lower holder Unscrew steering shaft holder bolt remove steering shaft holder Take off the cotter pi...

Page 38: ...nd oil seal tighten with the nuts Torque 33 N m 24 lbf ft Install the steering shaft nut and tighten it This nut is under this steering shaft Torque 50 N m 37 lbf ft Installation of Tie rod Install th...

Page 39: ...pressure FRONT WHEEL WOBBLING Faulty tire Worn front brake drum bearing Bent rim Axle nut not tightened properly BRAKE DRAG Incorrect brake adjustment Sticking brake cable STEERS TO ONE SIDE Bent tie...

Page 40: ...tighten the four wheel castle nuts Torque 40 60 N m 30 45 lbf ft Remember put a cotter pin in the castle nut 9 4 FRONT BRAKES FRONT BRAKE INSPECTION Remove the front wheel Remove the brake drum Measur...

Page 41: ...gs BRAKE PANEL REMOVAL Disconnect the brake cable from the brake arm Remove the brake panel from the knuckle Remove brake arm and cam Remove return spring Remove indicator plate and felt seal INSTALL...

Page 42: ...N m Install the return spring Install the brake panel on the knuckle Connect the brake cable to the brake arm Install the brake arm cover Tighten the screws securely Position the brake shoes in their...

Page 43: ...WHEEL AND BRAKE SYSTEM 10 1 PARTS DRAWING 10 3 DRIVE MECHANISM 10 2 TROUBLESHOOTING 10 4 HYFRAULIC DISC BRAKE SYSTEM 10 1 THE PARTS DRAWING OF REAR WHEEL SYSTEM FOR ATV RXL70 AND RXL50M FOR RXL 50 70...

Page 44: ...NG HOLDER IS FAULTY 10 2 TROUBLESHOOTING BAD BRAKE PERFORMANCE BRAKE SHOES ARE WORN BRAKE DRAG INCORRECT BRAKE ADJUSTMENT STICKING BRAKE CAM STICKING BRAKE CABLE 10 3 DRIVE MECHANISM REMOVAL AND INSPE...

Page 45: ...ning of bearing with fingers The bearings should turn smoothly and quietly Replace if necessary INSTALLATION Add grease to the dust seal lips and install dust seals Assembly the rear axle and the driv...

Page 46: ...st rear brake level free play Adjust chain slack 10 4 HYFRAULIC DISC BRAKE SYSTEM To replace brake disc To replace brake disc Remove the rear left tire Unscrew the two bolts shown on the photo and rem...

Page 47: ...rake disc Check the thickness of disc and replace a new one if the thickness less than 3mm TO REPLACE THE BRAKE SHOE Remove the rear left tire Unscrew the two bolts shown on the photo and remove calip...

Page 48: ...Check the thickness of brake shoe and replace a new one if the thickness less than 1mm Press the piston to the end prior to installation of brake shoe Piston TO REPLACE THE BRAKE HYDRAULIC OIL Unscre...

Page 49: ...ely Add the brake oil Dot 3 or Dot 4 Keep oil level at least half of the cup to avoid air gets into brake system such like caliper and tube Unscrew the bolt to vent air from brake system Fasten the bo...

Page 50: ...Fill the brake oil to the level shown on the cup when no air comes out Assemble the cover...

Page 51: ...DRAWING For YukonST EXL 50 For ViperST EXL 50 EXHAUST PIPE For all serials 11 1 FENDRES DRAWING 11 4 CENTRAL REAR TRIM REMOVAL 11 2 REAR FENDERS REMOVAL 11 5 FRONT FENDER REMOVAL 11 3 FRONT TRIM REMO...

Page 52: ...he rear fender Remove the rear rack Unscrew the two bolts which connect the front fender and rear fender Unscrew the two bolts which connect the rear tender and frame these two bolts just below the se...

Page 53: ...screws on side of the tail Finally you must remove the screws on the footrest 11 3 FRONT TRIM REMOVAL Unscrew the two screws just below the headlight of central front trim Unscrew the two screw which...

Page 54: ...ank cap Remove the central rear trim two mounting bolts from the fuel tank Pull the central rear trim up ward 11 5 FRONT FENDER REMOVAL After remove the rear fender central front trim and central rear...

Page 55: ...the headlight Then you can see there is a screw on the tip of the vehicle Please remove it And there are the screws on the both side of the vehicle You can see it inside of the front fender After you...

Page 56: ...Installation is the reverse order of removal Torque Exhaust muffler bolts 30 N m 22 lbf ft After installation make sure that there are no exhaust leaks 11 6EXHAUST PIPE REMOVAL For E MARK You must wai...

Page 57: ...UT RUNS POORLY IGNITION PRIMARY CIRCUIT Faulty generator Faulty CDI unit Faulty alternator exciter coil Loosen contacted terminals Faulty ignition coil IGNITION SECONDARY CIRCUIT Faulty plug Loosen co...

Page 58: ...OR EXCITER COIL Remove the seat rear fender and front fender see chapter 10 Disconnect the exciter coil wire Measure the resistance between the yellow red wire and ground STANDER 460 700 AT 20 68 12 3...

Page 59: ...t the terminals with clean grease 12 5 CHARGING Connect the charge positive cable to the battery position terminal Connect the charge negative cable to the battery negative terminal Using 0 9A chargin...

Page 60: ...is fully charged and in good condition 12 7 LIGHT BULBS REPLACEMENT HEADLIGHT For Viper St EXL 50 After you remove the screws on the top of headlight it can be take off Be careful around the headligh...

Page 61: ...HT Install the remove parts in the reverse order of remova For Viper St EXL 50 For YukonST EXL 50 12 8 SPEED METER AND FUEL METER PARTS DRAWING Picture of right side is for YukonST EXL 50 For Viper ST...

Page 62: ...T PHOTOGRAPH EXL 150 2004 two passengers EXL 150 Viper St have another shape but its cables position are the same as EXL 150 2004 two passenger ELECTRICAL SPEEDMETER FUEL METER CABLE METER SENSOR METE...

Page 63: ...12 9 WIRING DIAGRAM This diagram is for Viper St EXL 50...

Page 64: ...This diagram is for YukonST EXL 50...

Page 65: ...el tube Faulty spark plug Fouled spark plug Faulty CDI unit Faulty alternator Faulty engine stop switch Poorly connected broken or shorted wires Broken or shorted ignition coil Broken or shorted spark...

Page 66: ...rated insulator o ring Loose carburetor PERFORM SPARK TEST WEEK OR INTERMITTENT SPARK Loose or disconnected ignition system wires Faulty carbon or wet fouled spark plug Faulty alternator Faulty CDI un...

Page 67: ...ire Faulty tire valve Fuel air mixture ratio too rich or lean Clogged in air cleaner Clogged in muffler Restricted fuel flow Clogged fuel tank cap breather hole TEST CYLINDER COMPRESSION O K ACCELERAT...

Page 68: ...Damaged steering bearing Damaged steering shaft bushing Bent rim Improperly installed wheel hub Excessive wheel bearing play Bent swingarm Bent frame Swing arm pivot bushing excessively Worn Bent tie...

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