Yamaha JT1 Series Service Manual Download Page 1

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Summary of Contents for JT1 Series

Page 1: ... tr c YAMAHA JT1 JT2 SERIES SERVICE MANUAL ...

Page 2: ...n of the requisite basic product knowledge Other information is produced by the U S distributor Yamaha International Corporation and is necessary to provide total technical coverage regarding the product The Research Engineering and Service Departments of Yamaha are continually striving to further improve all models manufactured by the company Modifications are therefore in evitable and changes in...

Page 3: ...ged design and excellent performance also make it an intriguing d1vers1on for older more exRerienced riders as well This service manual has been prepared 1n order to provide all Yamaha dealers and their service techn1c1ans the repair 1nstruct1ons and technical information required to keep the MINI ENDURO in top cond1t1on We hope that you will find this manual most helpful and valuable in carrying ...

Page 4: ...he JT2 had various internal engine changes to improve reliability and carburetor changes to improve performance JT2 lights were upgraded in intensity The JT2M was styled after the JT1 for those people who wanted a Mini motocrosser without lights Additional identification information is given in the table below IBM ID STARTING IDENTIFYING MOOEL YEAR NUMBER ENGINE NUMBER COLOR JT1 1971 288 JT1 00010...

Page 5: ...Handling the Oil Pump 7 CHAPTER 3 ENGINE 1I 3 Engine Remova1 I 1 3 2 Cylinder Head 15 3 3 Cylinder 16 3 4 Piston Pin 17 3 5 Piston Ring 18 3 6 Piston 19 3 7 Flywheel Magneto 20 3 8 Crankcase Cover RH 21 3 9 Clutch 22 3 10 Primary Drive Gear 27 3 11 Kick Starter Mechanism 27 3 12 Shift Mechanism 29 3 13 Rotary Valve 31 3 14 Drive Sprocket 33 3 15 Crankcase 35 3 16 Transmission Assembly 36 3 17 Cran...

Page 6: ...CAL SYSTEM 62 5 1 Electrical Equipment 62 5 2 List of Electrical Components 62 5 3 Ignition System Function and Service 63 5 4 Ignition Timing 63 5 5 Ignition Coil 64 5 6 Condenser 64 5 7 Charging System 65 5 8 Battery 67 5 9 Checking the main Switch 69 5 10 Spark Plug 69 APPENDICES 72 I Parts and Service Bulletins 72 II Parts Illustrations 82 Ill Maintenance and Lubrication Intervals 86 IV Pre op...

Page 7: ...ct a w z w w a C I w 8 a I w I a ct c c 7 OVERALL WIDTH 27 6 700 I GROUND LEVELIW 0 RIDER i 31 5 800 r7 9 200 M WHEELBASE 41 5 1 055 I j JVERALLENGTH 62 0 1 575 4 DIMENSIONS PROFILES TYPICAL FOR ALL MODELS 0 e N ri N ...

Page 8: ...I I Front fork Chain guard Muffler Side stand magneto Sprocket Rear wheel Tail light JT L Light Rectangular I r I 1c i ...

Page 9: ...aking distance 24 6 ft 22 mph 7 5 m 35 km h Engine Model JT1 Type 2 stroke gasoline Lubricating system Separate lubricahon YAMAHA Autolube Cylinder Single forward inclined Displacement 3 54 cu n 58 cc Bore x Stroke 1654 in x 1654 in_ 42 mm x 42 mm Compression ratio 6 4 1 Max power 4 5 hp 7 500 rp m Max torque 3 62ft lb 5 500 r p m 0 5 k9 m 5 500 rpm Starting system Kick starter Ignition system Mag...

Page 10: ...m front Telescop1c fork Suspension system rear Swmging arm Cushion system front Coil sprmg oil damper Cushion system rear Coil sprmg 011 damper Steering system Steering angle 4 7 both right and left Caster 63 5 Tra1 2 7 in 68mm Brakmg system Type of brake Internal expansion Operation system front Right hand operation Operation system rear Right foot operation Tire size Front 2 50 t5 4PR Rear 2 50 ...

Page 11: ...m Ma ii imum Torque 3 62 ftlbs 5 S00rpm I Horse power I I Torque r V _ I I I I Fuel consumption 3 2 w 0 I 0 z 0 ii i 500 400 8 J 300 2 000 3 000 4 000 5 000 6 000 7 000 8 000 9 000 10 000 ENGINE SPEED rpm 3 port Cylinder Exploded View 0 22 0 N 0 I l I I ti _ N _ I I 19 5 0 D D I _ 24 0 1l __ _ ____ Exhaust port tran sfer par Inlet port 5 ...

Page 12: ...r S 14 Slot head screwdriver M 15 Slot head screwdriver S 16 T handle socket wrench 2 Special Tools and Instruments I Clutch holding tool 2 Crankcase disassembling tool 3 Crankshaft assembling tool 4 Flywheel magneto holding tool 5 Flywheel magneto puller Fig 1 6 1 F g t 6 2 In addition an electro testor tachometer engine rpm meter hy drometer etc should and available 3 Other Material 1 Yamaha Bon...

Page 13: ...of oil for engi_ne ubncation under any operating condition This automatic separate lubrication does not merely eliminate disadvantages in the conventional pre mix system but 11 further improves the perform nce and efficiency of 2 stroke designs by eliminating certain oil starvation conditions which formerly existed The Autolube feeds an optimum amount of lubricating oil to the engine under any ope...

Page 14: ... starter plate in the direction of the arrow marked on the plate Then measure the gap between the adjustment pulley and the adjustment plate Keep the gap as wide as possible by observing lt with the eye prior to measuring c Insert a feeler gauge 015 mm into the gap If the qap allows it to enter Stroke Is correct If the gap does not allow Stroke is insufficient 2 Adjustment a Remove the adJustment ...

Page 15: ...st the carburetor with the engine at td e and remove all but 1 mm of slack from cable B 9 To bring the play of the throttle cable into correct adJustment loosen or tighten the throttle cable adiustment screw To check this adiustment lightly pull throttle cable B and engine speed should slightly increase from 1dlmg r p m after 1mm of travel b Next adJust throttle cable A so that the gap as shown in...

Page 16: ...ovide clearance 2 3 3 Bleeding Lock nut Guide pin Fig 2 3 7 When the pump has been removed or the Autolube oil has run out air will enter the pump The air will cause an irregular flow of oil after the pump 1s mounted again or the 01 tank 1s refilled In order to prevent such an irreg ular flow of oil b leed the pump in the following manner I Remove the bleeder bolt 2 Next rotate the starter plate i...

Page 17: ...embly before removal and disassembly This will prevent any harmful foreign material from entering the interior of the engine assembly 2 Before engine removal and disassembly be sure you have proper tools and cleaning equipment so you can per form a clean and efficient job 3 During disassembly of the engine clean all parts and place them in trays in order of disassembly This will make assembly time...

Page 18: ...d lift the fuel tank off 4 Remove the connector from the magneto lead wire and remove the plug cap 5 Remove the muffler a Remove the exhaust pipe nut Use the special wrench Hammering on the nut will only damage it and or the cylinder b Remove the muffler holding bolts 13 mm 12 F g 3 1 3 Fig 3 1 4 Fig 3 1 5 Fig 3 1 6 ...

Page 19: ...3 1 8 8 Disconnect the master link and remove the chain Fig 3 1 9 When reconnecting the chain be sure the master link is facing in the correct direction driving direction After reconnecting the chain adjust the free play to 25 mm 1 in up and down at the center of the lower section with the rear wheel on the ground 13 ...

Page 20: ...Y_tdriver 10 Remove the oil pipe and plug the hole with a bolt to stop the flow of oil from the tank Remove the fuel line and remove the carburetor 8 screwdriver 12 Remove the four engine mounting bolts 13 mm Fig 3 1 13 Fig 3 1 10 Fig 3 1 11 Fig 3 1 12 Fig 3 1 14 14 ...

Page 21: ...ote During reassembly the head bolts must be torqued to 90 rn lbs rn pattern and in successive stages Do not torque a hot engine and for most accurate readings_ place a small amount of light we ght oil on the threads first Fig 3 2 1 8 Removing Carbon Deposits Carbon deposits on the cylinder head combustion chamber and top of the piston will result in an increase in the compression ratio as well as...

Page 22: ...ount of wear of the cylinder wall with a cylinder bore measuring micrometer or cylinder gauge Measure it at four depths while posit1on1ng the instrument parallel and then at riQht angles to the crankshaft If the difference between the maximum and minimum diameter exceeds 0 05 mm 0 0019 rebore and hone the cylinder 0 s 0 0 a b D c 1 1 d 2 The piston clearance between the piston and the cylinder is ...

Page 23: ... the exhaust port of the cylinder with the dulled end of a hack saw blade E Installing the Cylinder Put your fingers at each end of the piston ring expand the ring and slip it onto the piston Align both ends of the ring with the knock pin m eac h rmg groove Next slip the cylinder down over the piston Compress the rings to prevent ring breakage during installation 3 4 Piston Pin A Pulling out the P...

Page 24: ...aring F g 3 4 2 Fig 3 4 3 3 5 Piston Ring A Removing the Piston Rings Put your thumbs at each end of the piston ring and pull the piston ring ends apart Remove the nng by moving the ring off the piston on the other side of the ring ends and lifting up F g 3 5 1 B Installing the Piston Rings First flt No 2 nng over the piston and then the No 1 ring and align their end gaps with the locat ing pin in...

Page 25: ... Checking and Correcting the Piston to Cylinder Wall Clearance 1 Measuring piston clearance Piston clearance is the difference between the minimum cylinder bore diameter and the maximum outside diameter of the piston As described in 4 3 Cylinder piston clearance should be 0 040 0 04Smm 0 0016 0 0018 To determine the maximum piston diameter measure the piston with a micrometer at right angles to th...

Page 26: ...damaged Carbon and gum accumulations in the piston ring grooves will result in piston ring seizure Remove them from the ring groove B Piston Installation Direction Install the piston with the arrow mark on the head pointing forward toward the exhaust port of the cylinder 3 7 Flywheel Magneto A Remove the nut using a flywheel magneto ho dmg tool to hold the magneto and a 19 mm socket to loosen it F...

Page 27: ...e fly wheel magneto base D Remove the woodruff key It is advisable to place the woodruff key on the flywheel magnets using its magnetic force while the key is removed for engm e service This will keep it from becoming lost 0Screw driver hammer 3 8 Crankcase Cover R H A Removal 1 Remove the kick crank mounting bolt and the crank 10 mm ENGINE Flywheel Magneto Crankcase Cover Fig 3 7 2 Fig 3 7 3 Fig ...

Page 28: ...crankcase cover R Be sure to apply YAMAHA Bond No 5 to the mating sur face otherwise the crankcase will leak Note When ir alling the crankcase cover R make re that the pump drive gear made from sYnthetic resin 1s correctly engaged with the primary drive gear_ In addition make certain that all mating surfaces have been thoroughly cleaned 3 9 Clutch Fig 3 8 4 The clutch is of the wet disc type consi...

Page 29: ...ch spring 8 Spring screw 9 Push rod t 10 Lock nut 11 Lock washer 12 Spacer 13 Thrust plate 14 Ball 15 Push rod 2 16 Kick pinion gear Fig 3 9 1 Clutch ass y exploded view A Removing the Pressure Plate Remove the four clutch spring holding screws and take out the pressure plate and push crown 8 Screwdriver Fig 3 9 2 Fig 3 9 3 23 ...

Page 30: ...r more shorter than the standard free length replace it Slide calipers Free length 34 mm 1 340 m D Checking the Friction Plates Measure the fnct1on plate at several points for wear Replace it if it is worn more than 0 35mm 0 0137in or more Also replace 11 1f uneven contact 1s quite evident Slide calipers Standard thickness 3 5 mm 0 137 in Wear limit 3 15 mm 0 124 in 3 5 mm Standard Thickness I Fig...

Page 31: ...the spacer to avoid impaired clutch action F Checking the Primary Gear Retaining Collar Spacer Place the prim ry gear retaining collar around the main axle and again check it for radial play If play exists allowable clearance is between0 020 0 062 mm replace the gear_ retaining collar Replace any collar with step wear on its outer surface G Checking the Push Rod ENGINE Clutch Fig 3 g Fig 3 9 8 Rem...

Page 32: ...anism left side of the engine Looking at the inside of this cover you will see the clutch actuating arm Push the arm up and lift the cable end off Removing the old cable and hooking up the new one will take but a few moments CLUTCH CABLE ADJUSTMENT The clutch lever should have 080 to 120 in 2 to 3mm free play to maintain full pressure against the clutch facing If the play is excessive the clutch w...

Page 33: ...hanism 3 10 Primary Drive Gear A Removal Feed a rolled up rag between the teeth of the primary drive gear and the primary driven gear to lock them and loosen the primary drive gear lock nut The primary gear can then be forced off Fig 3 10 1 27 ...

Page 34: ...es nmse resulting from the constant mesh of the kick gear with the idler gear but also greatly contributes to the durab1hty of the kick starter assembly Fl 1 INSTALLED KICK STARTER I 16 Fig 3 11 1 18 KICK STARTER COMPONENTS Fig 3 11 2 It 17 28 8 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 I 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 Kick pinion gear Kick idle gear Thrust washer Circhp Shim Circlip K...

Page 35: ...l 1s moved the gear shift arm A 1s moved back or forward by the gear sh 1ft arm B see Fig 3 12 1 The gear shift drum pm attached to the gear shift drum is pushed by the gear shift arm A and the gear shift drum begms to rotate A total ot live gear shift drum pins are attached to the gear shift drum When the change pedal 1s moved the unit is designed to shift through five stages Neutral Low Second T...

Page 36: ...e Change Axle Assembly Fig 3 t2 2 I Gear shift arm B 2 Gear shift arm spring 3 Gear shift arm A 4 Gear shift drumpin 5 Shift drum stopper spring 6 Shift drum stopper lever 7 Shift fork 8 Gear shift drum 9 Change pedal 10 Change axle Ass y 11 Gear shift spring 1 Remove the circlip and washer from the change axle left side crank case 8 Screw driver 2 Turn the engine over right side up and pull out t...

Page 37: ...f the gear shift arm to prevent improper shifting progression excess feed or insufficient feed of the gear shift arm is accomplished by turning the gear shift return spring stop screw eccentric bolt m or out In second or third gear the measurement A A must be equal 8 Screwdriver 3 13 Rotary Valve A Removal 1 Remove the six valve cover set bolts and remove the valve cover f Screwdriver ENGINE Shift...

Page 38: ...ck for looseness If 1t 1s foun d too loose replace it If the collar is found to have step wear due to locating pin friction 1t should be replaced 2 The 0 ring 1s subJect to stretch flatten mg or hardening after a long period of use Any stretched or aged 0 ring may fail to snugly fit in the groove If it 1s found defective 1t Slould be replaced with a new one When installing it grease it Fig 3 13 2 ...

Page 39: ...urface of the inner collar and the outer surface of the 0 rmg 4 When 1nstalltng the valve cover applygood quality grease to the lip so 1t will slip easily over the shaft 3 14 Drive Sprocket A Removal 1 tra1ghten the bent edge of the lock washer with a blunt ended metal punch Flat chisel F g 3 13 6 F g 3 13 7 Fig 3 14 1 33 ENGINE Rotary Valve Drive Sprocket ...

Page 40: ...h with a hammer and the shock will loosen the nut The best method of removal is an air impact wrench 21 mm 3 Remove the distance collar with pliers When re installing the distance collar apply grease to the oil seal lip groove B Inspection Fig 3 14 2 Fia 3 14 3 A worn drive spr9cket will result in excessive chain noise and shorten the life of the chain Check the sprocket for worn teeth and replace...

Page 41: ... stopper spring 10 mm 3 Remove the twelve pan head screws from the left crankcase EB Screw driver ENGINE Crankcase Fig 3 15 1 Fig 3 15 3 4 Install the crankcase separating tool on the right crankcase Divide the crankcase while alternately tapping the main axle and the crankcase with a soft faced hammer 35 ...

Page 42: ...em thoroughly 3 16 Transmission Assembly Fig 3 15 7 The constant mesh wide ratio 4 speed transmission makes it possible to fully utilize the steady performance of the engine throughout the entire speed range from low to high speed For layout of the transmission and related parts refer to Fig 3 16 1 and 2 The primary reduction ratio is 74 19 3 894 Therefore the total reduction ratios will be Primar...

Page 43: ... gear 6 Circlip 7 Bearing 8 Bearing cover plate 9 Bolt 10 Drive axle 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 4th wheel gear Distance collar 2nd wheel gear Circlip 3rd wheel ge ar 1st wheel gear Shim Circlip Thrust washer Wave washer Kick idle gear Circlip Bearing Oil seal Distance collar Drive sprocket Lock washer Nut ...

Page 44: ...embly from the crankcase while tapping the drive shaft end with a soft faced hammer B Reinstallation Reinstall the transmission and shifter as a unit in the left crankcase half afte r they are sub assembled They cannot be installed separately The transmission unit must be in neutral during installation Fig 3 16 3 Fig 3 16 4 Fig 3 16 5 38 ...

Page 45: ... care 12 13 Frg 3 17 1 2 Fig 3 17 2 Crankshaft compon ent parts 3 39 1 Cylinder head 2 Piston 3 Piston ring 4 Piston pm 5 Piston pm c 1p 6 Cylinder body 7 Connecting rod 8 Crank pm 9 SW28 47 8 10 Crank R H 11 Distance collar 12 Crank 13 SO20 40 8 1 Cran left 2 Crank right 3 Rod connecting 4 Bearing con rod big end 5 Pm crank 6 Bearing con rod small end 7 Pm dowel ...

Page 46: ...tion and Servicing 1 Checking the crankshaft components F g 3 17 4 Check connecting rod axial play at Small end play should not exceed the small end to determine the amount 2 mm 0 078 in of wear of crank pin and bearing at large end F1g 3 17 5 Check accuracy of the crankshaft Dial gauge readings should be ass y runout M isalignmenl of parts within 0 03 mm 0 0012 in of the crankshaft F1g 3 17 6 F g...

Page 47: ...ing the engine 0 Screw driver b Drive out the bearing with a bearing tool It is preferable to heat the case to approxi mately 120 c 250 F to remove bearings 2 Installation ENGINE Bearings and Oil Seals Bearing 6303 F g 3 18 2 Fig 3 18 3 Install bearings and oil seals with their stamped manufacturers marks or numerals facing outward In other words the stamped letters must be on the exposed view sid...

Page 48: ...t 5 Float 6 Gasket 7 Float chamber body 8 Spring washer 9 Pan head screw 10 Body fitting screw 11 Air adjusting spring 12 Air adiusting screw 13 Valve seat assembly 14 Throttle valve 15 Throttle bar 16 Needle 17 Plunger starter assembly 18 Plunger spring 19 Cl p 20 Spring seat 21 Throttle valve spring 22 Mixing chamber top 23 Throttle stop spring 24 Throttle screw 25 Cotter pin 26 Wire adjusting n...

Page 49: ...3 Overflowing If fuel overflows check the carburetor as described in 1 and 2 above If neither 1 nor 2 cures the overflowing it may be caused by dirt or dust in the fuel preventing the float valve from seating properly If any dirt or dust is found clean the carburetor petcock and gas tank Valve seat L LFloat F g 3 19 2 4 Cleaning the carburetor Disassemble the carburetor and wash all its parts in a...

Page 50: ... location and cond1t1on of the inlet needle seat on the top of the float If 11 Is in good cond1t1on float level w11 be correct This Is due to the fact that as fuel level increases the float 1s raised until 11 touches and then shuts off the inlet needle There Is no float arm or shut off tang as found on other Yamaha models 3 20 Air Cleaner This model is equipped with a reuseable oil impregnated foa...

Page 51: ...it After washing shake off the excess solvent and install the element in the case Never allow the element to dry out as its efficiency will be greatly reduced 2 AIR CLEANER 7 9 8 4 5 JT2 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Air cleaner case cop Air cleaner element Air cleaner case Bond Air cleaner ioint Pon head screw Crown nut Washer Pan head screw Spring washer Leg shield washer 2 Battery box damper...

Page 52: ...l tire This tire gives the rider assurance of maximum performance and safety for both road riding and trail riding The front wheel brake size 1s 110 mm x25 mm 4 33 xo 98 m A labyrinth seal 1s installed between the wheel hub and brake plate to provide a seal against dust and water 15 1 Hub 16 2 Spoke set 12 3 R m I I 4 Front tire Jl I 5 Tube 6 Rim band 7 Spacer 8 Bearing 9 Oil seal 10 Oil seal 11 D...

Page 53: ...e front wheel nut 17 mm 3 Pull out the front wheel shatt Take care not to lose the distance collar as 1t will come loose when the shaft 1s removed 4 Raise the front of the machine and set it on a box Then remove the wheel assembly 47 CHASSIS Front Wheel Fig 4 1 3 Fig 4 1 4 Fig 4 1 5 ...

Page 54: ...m 4 09 in replace 1t 3 Brake drum Oil or scratches on the mner surface of the brake drum will impair braking performance or result in abnormal noises Clean or smooth out the surface with a rag soaked in lacquer thmner or with sand paper Fig 4 1 6 Fig 4 1 7 Fig 4 1 8 I 0 Dial Q lUge rMAX 2mm r 0 07 in 4 Check the spokes If they are loose or bent replace or tighten them If the machine 1s ridden in r...

Page 55: ...clean the outside of the wheel hub CHASSIS Front Wheel Rear Wheel Fig 4 1 9 b Insert the bent end of the special tool as shown in Fig 4 1 11 into the hole located in the center of the bearing spacer and drive the spacer out from th0 hub by tapping the other end of the special tool with a hammer Both bearing spacer and spacer flange can easily be removed c Then push out the bearing on the other sid...

Page 56: ...Hob 2 Spol1e set 3 R m 4 Rear 1 re 5 Tube 6 R m band 7 Bearing soacer 8 Spacer flange g Bear ng 10 Q I e JI 11 8e ir1n9 13 12 8r Jke shoe pl 13 C 1m shah 14 Brake shoe comp 15 Re1urn spnng 18 Cam shu 1t lever 17 Bolt 13 Not 19 Washer 20 Clutch hub 21 Lock wash 22 Boll 23 Sproci et wheel geBr 24 Wheel shah 25 Chain puller 26 Shaft collar 27 Oil seal 28 Shaft collar 29 Cham puller 30 Shilft nut 31 N...

Page 57: ...ate F g 4 2 2 2 Loosen the chain tension adJusting nut and bolt on both right and left sides 10 mm 3 Remove the rear wheel shaft nut 19 mm 4 Pull out the rear wheel shaft by striking it with a soft faced hammer 51 F g 4 2 3 F g 4 2 4 F g 4 2 5 F g 4 2 6 CHASSIS Rear Wheel ...

Page 58: ...it is the front tire or the rear tire to be changed the procedure of tire and tube removal 1s 1dent1ca The explanation that follows 1s the proper method for both wheels b Remove the wive cap valve stem and valve stem lock nut Use two tire irons with rnunded edges and begin to work the tire bead over the edge of the rim starting opposite the tube stem Take care to avoid p1nchinq the tube After one ...

Page 59: ...eck the rim for run out in the same way as the front wheeL Maximum limit of runout 2 mm 0 07 in or less 2 Brake shoe Check the brake shoe in the same way as the front wheel Wear limJt 124mm 4 9 in 3 8rake drum Check the brake drum in the same way as the front wheel 4 The spokes are measured in the same way as the front wheel A loose spoke should be tightened 5 If the bearing has excessive play or ...

Page 60: ...tom of the chain at a point midway between the drive and driven axles 3 Turn adjusting nuts in or out to obtain correct free ploy and at the some time insure that both ends of axle ore posi tioned evenly This con be checked by utilizing the morks on end of swing orms ond notch cut into top of adjusting bolt Tighten the rear axle securing nut Axle Nut Torque 4 5 5 0 kg m 400 440 in lbs 4 4 Tires an...

Page 61: ...the mner tube cap bolt 17 mm 3 Loosen the mner tube pinch bolt on the under bracket 14 mm 4 Pull the outer tube downward B Disassembling the Inner and Outer Tubes 1 Dram the oil from the fork Fig 4 5 3 Fig 4 5 5 55 CHASSIS Front Forks ...

Page 62: ...once this tube nut 1s threaded off Fig 4 5 6 2 6 1 Fig 4 5 7 Front Fork Exploded View 56 1 2 3 4 5 6 7 8 9 to t 1 12 13 14 15 16 17 18 19 Outer right tube 0 ring Fork spring Spring upper washer Spacer Inner right tube Slide metal Outer nut comp Oil seal Dust seal Packing Cap washer Cap bolt Outer left tube Underbracket bolt Spong washer Inner left tube Underbracket comp Front fork guide ...

Page 63: ...in and out smoothly 2 1nstalling the front fork on the frame a Bring up the front fork to the correct position and tighten the underbracket pinch bolt slightly Fill the fork tube with oil see below and tighten the cap bolt thoroughly Then tighten teh pinch bolts completely b Pour oil into the inner tube through the upper end opening Frant fork oil Yamaha shock fluid Right 97 cc 3 3 fl oz Left 120c...

Page 64: ...by pulling 1t backward 2 Set the petcock lever at the Stop pos1t1on and disconnect the fuel line at the petcock Fig 4 6 2 Fig 4 7 1 Fig 4 7 2 3 Next remove the tank holding bolt and remove the tank by pulling it backward 13 mm 4 8 Rear Swing Arm The rear swing arm is made of steel tubing that improves the strength and torsional rigidity The pivOl employs permanently lubricated bearings 58 ...

Page 65: ... Frg 4 8 1 Frg 4 8 2 1 Check the play of the rear swing arm by shaking 1t as show in Fig 4 8 3 with the rear swing arm installed If the play 1s excessive replace the rear swing arm bushing or the rear swing arm shaft 2 lnsert the bushing as indicated in Fig 4 8 4 and check it for play It the play is excessive replace the bushing Fig 4 8 3 Fig 4 8 4 3 Grease the rear arm shaft periodically 59 ...

Page 66: ...oll race cover Handle crown Handle upper holder Handle under holder Nut Plain washer Spring washer Bolt Spring washer Fitting nut Crown washer Fitting bolt Boll race If 2 Bal I race ft l Ball inch Check the ball races and steel balls for pitting or wear_ Check them very carefully If the machine has been m long use I any are worn or cracked replace all of them because defective ball races or steel ...

Page 67: ... steel tubes that provide strength rig1d1ty and light weight Other d1mens1onal features include high ground clearance narrow width and long wheelbase The engine s bolted to the frame at three pos1t1ons The caster 1s measured at 63 50 Fig 4 tl 1 4 12 Handlebars The upswept type longer handlebars are ideal for leverage on rough terroin and ore provided with deep cut pattern grips to prevent hand sli...

Page 68: ...tifier Horn Ignition coil Fuse holder Front End Headlight Speedometer Rear End Taillight stop light Stop switch Manufacturer Hitachi Ltd NGK Hitachi NGK Asahi Elec GS Asahi Elec Fuji Elec Nikko Hitachi Elec Mitsuba Elec Koito Elec Nippon Seiki lmasen Elec Asahi Elec NOTE See Appendices for JT1 L components 62 Model Type F11 L42 B 7HS F11 L46 Sparking 7mm or more 500 rpm 8mm or more 5 000 rpm Charg...

Page 69: ...he electric spark jumps across the spark plug electrodes High tension wire Ignition coil Flywheel Fig 5 3 1 5 4 Ignition Timing Remove the spark plug and screw the dial indicator holder into the plug hole Next insert the dial indicator into the holder Bring the piston up to T D C and set the zero on the dial face to line up exactly with the dial indicator needle The crankshaft should then be turne...

Page 70: ...pproximately 7 mm away from the head and see if it sparks as you crank the kickstarter If it sparks at 7 mm or so and has blue white color the ignition coil should be considered to be in good condition 5 6 Condenser The condenser instantly stores a static electric charge as the contact breaker points separate and the energy stored in the condenser discharges instantly when the points are closed If...

Page 71: ...he tester to the condenser capacity The tester should be connected with the condenser in the same way as in the case of the insulation resistance test Before this measurement be sure to set the tester correctly If the reading is within 0 22µF 10 the condenser capacity is correct 5 7 Charging System JT2 See Appendices for JTll information The charging system consists of the flywheel magneto chargin...

Page 72: ...ully charged If the battery is in a low state of charge and low in voltage the charging rate v ill be not exactly the same as above However it is desirable that the figures are as close as possible 2 Silicon Rectifier The alternating current which is generated by the flywheel magneto is rectified and charged to the battery For this rectification a single phase halfwave silicon rectifier is employe...

Page 73: ...ctifier is in good condition If the pointer swings the rectifier is faulty 3 Operational Note The silicon rectifier can be damaged if subjected to overcharging Special care should be taken to avoid a short circuit and or incorrect connection of the positive and negative leads at the battery Never connect the rectifier directly to the battery to make a continuity check 5 8 Battery JT2 The battery i...

Page 74: ...ling the battery with electrolyte 21 Batte y beirg left discharged 3 Over charging by rushing charge 4 Freezing 5 Fe8ding of water or sulfuric acid containing impurities when re filling the battery 3 Storage If any motorcycle is not used for a long time remove the battery and have it stored by a battery service shop The following instructions should be observed by shops eauipped with chargers 11 R...

Page 75: ...as well as betv 1een the lead terminal and the switch body the main switch is in good condition 5 10 Spark Plug The nte of a plug and its discoloring very according to the habits of the rider At each periodic inspection replace burned or fouled plugs with suitable ones determined by the color and condition of the bad plugs One machine may be ridden only in urban areas at low speeds whereas another...

Page 76: ...re to use standard B 7HS plug as replacements to avoid any error in reach or heat range 0 5 0 6mm 0 023 n l 5 11 Lighting and Signal Systems JT2 The lighting and signal systems consist of the horn and stop light power source battery and the head light tail light and meter lamps Power source flywheel magneto 1 Head light The head light has two 6V 1 5W bulbs and a 6V 1 5W neutral pilot light on its ...

Page 77: ...ket For illumination a 6 V 3 W bulb is provided SPARK PLUG JT1 JT2M II FLYWHEEL MAGNETO CONDENSER CONTACT BREAKER SOURCE COIL ENGINE STOP BUTTON JT1l HIGH BEAM r r fi Y LIGHT SWITCH 7 I L BR W I I I _ G ___ L ___ BR J LOW BEAM TAIL LAMP 111 i STOP LAMP FLYWHEEL MAGNETO ENGINE STOP BUTTON B JT2 FLYWHEEL MAGNETO NIGHT M C_ NIGHT ODAY HORN BUTTON 71 IGNITION COIL II STOP SWITCH SPARK PLUG DAY 0 NEUTR...

Page 78: ...S A GUIDE ONLY TO INDICATE THE DIRECTION TAKEN BY VARIOUS MODIFICATIONS IT IS INCLUDED ONLY AS AN AID TO SERVICING THE JT SERI ES AND SHOULD A QUESTION ARISE REGARDING A CERTAIN PART THE MECHANIC SHOULD REFER TO AN UP TO DATE MODEL PARTS BOOK SERVICE OR PARTS NEWS BULLETIN OR THE MANUFACTURER 72 ...

Page 79: ... the outer valve surface must line up with the pin in the crankshaft Rotary valve timing can also be checked by rotating the piston to top dead center indicated with dial indicator and checking that the valve closing edge just lines up with the left edge of the intake port see drawing PIN LOCATION NOTE The locating pin in the shaft is removable Although the pin hole is drilled thru the shaft permi...

Page 80: ...laboratory equipment supply house check local listing in telephone yellow pages and attach an Autolube delivery line to one end of the tube Leave the banjo fitting on the other end of the delivery line to provide a universal adaptor for all models B PROCEDURE Whether checking the pump on the machine or bench the procedure is identical 1 Disconnect original oil delivery line and attach graduated tu...

Page 81: ...4 19 X 62 1 HSlB so 63 4 20 4 80 Blue 34 19 X 62 1 YLl E so 63 4 20 4 80 Yellow 34 19 X 62 1 LST 50 63 4 65 5 15 Green 34 19 X 36 1 LSTA 50 63 4 65 5 15 Green 34 19 X 36 1 ATl 95 1 19 8 80 9 76 Yellow 28 19 X 55 1 ATlB MX 95 1 19 8 80 9 76 Yellow 28 19 X 55 1 ATlC 95 1 19 8 so 9 76 Yellow 28 19 X 55 1 AS2C so 63 4 17 4 80 Vvhite 34 19 X 55 1 CTl 95 1 19 8 80 9 76 Yellow 28 19 X 55 1 CTlB 95 1 19 8...

Page 82: ...80 9 76 Yellow AT2 M 95 1 19 8 80 9 76 Yellow CT2 95 1 19 8 80 9 76 Yellow DT2 95 1 19 8 80 9 76 Black DT2 MX 95 1 19 8 80 9 76 Black RT2 95 1 19 8 80 9 76 Green RT2 MX 95 1 19 8 80 9 76 Green TD3 TR3 NUMBER 258A PAGE 3 of 3 REDUCTlON RATIOS 68 19 X 56 1 28 19 X 55 1 34 19 X 62 1 28 19 X 40 1 28 19 X 40 1 20 16 X 55 1 22 21 X 40 1 21 23 X 32 1 30 19 X 62 1 30 19 X 62 1 30 19 X 62 1 28 19 x 55 1 28...

Page 83: ...tall new grommet bigger hole for loom see sketch 3 7 Re install stator 8 Route new wires with ignition wire B Main harness 1 Remove tank 2 Route alongside frame tube see sketches 1 and 2 C Handle switch 1 Remove left grip 2 Install switch 3 Re install grip NOTE The handle switch is a combined type similar to the DS3 switch Check the schematic page 4 carefully in order to wire correctly D Headlamp ...

Page 84: ...er rear engine mount right hand side 2 Insert switch rod in brake lever hole 3 Adjust as necessary H Connections 1 Main harness taillight leads and source wires terminate under seat 2 Use nylon clip to secure to righthand frame tube next to and over oil tank do not allow wires to touch muffler 3 Caution See sketches as otherwise shorts may occur 4 Hook up according to schematic page 4 5 Re install...

Page 85: ...00 92201 06100 00 290 82 530 00 00 290 82539 99 00 288 83973 00 00 214 83974 00 00 98503 05018 00 288 81313 10 00 288 82590 20 00 803 82591 00 00 DESCRIPTION JTl Lighting Kit comp HEADLAMP UNIT ASSY BODY WIRE Earth SCRE w STAY Headlamp STAY Headlamp BOLT WASHER BOLT WASHER WASHER NUT TAILLAMP UNIT ASSY BRACKET GROMMET BOLT NUT WASHER STOP SWITCH STAY Switch SWITCH Handle HOLDER Switch SCREW COIL L...

Page 86: ...to i 2 qty PARTS BOOK CORRECTION Origirlal JTl Parts Book picture on page 49 shows top and bottom bearing assemblies upside down Rearrange as in picture above PAGE 1 of l Fig No Descri12tion Old Part Number New Part Number Retail Disc 18 1 BALL RACE 2 282 23412 00 00 282 23412 01 00 1 94 A 18 16 BALL RACE 3 282 23412 00 00 288 23413 00 00 1 94 A add J2 Carburetor cap Fig No 2 20 The carburetor cap...

Page 87: ...2 AIR CLEANER COVER JOINT NUMBER 347 PAGE 1 of 1 The metal retaining cover for the rubber air cleaner joint is now available from the Parts Department Please update your JT2 JT2 MX Parts List to include this part PARTS ORDERING Ref No Part Number Description Price 9 15 288 14417 00 00 COVER Joint 1 Add 81 ...

Page 88: ...t 19 Breather 20 Rubber ring 21 Valve cover 22 0 ring 23 0 ring 24 Dowel pin 25 Pon head screw 26 Blind plug 27 Gasket Fig II CRANK PISTON 15 16 b Fig I CRANKCASE CYLINDER FIG II CRANK AND PISTON 1 Left crank 2 Right crank 3 Connecting rod 4 Con rod big end bearing 5 Cronk pin 6 Con rod small end bearing 7 Piston 8 Piston pin 9 Piston pin clip 10 Piston ring set 11 Bearing 12 Dowel pin 13 Valve 14...

Page 89: ...asher 9 Protector washer IQ Exhaust gasket I I Bolt 12 Spring washer 13 Plain washer 14 Gasket Ql 83 APPENDIX II FIG 111 JTI MUFFLER I Exhaust pipe assembly 2 Outlet pipe 3 Bolt 4 Spring Wosher s Chain case washer 6 Muffler protector 7 Bind Screw 8 Protector washer 9 Protector washer 10 Exhaust gasket Bolt 12 Spring washer 13 Plain washer 14 Gasket Fig IV EXHAUST ...

Page 90: ...r assembly 10 Plain washer Source coil 11 Condenser Lighting coil 12 Pan head screw Pan head screw 13 Spring washer Spring washer 14 Lubricator Timing plate 15 Lead damp Contact breaker 16 Pan head screw assembly 17 Spring washer Pan head screw 18 Fl at head screw Spring washer Fig V FLYWHEEL MAGNETO l l 5 JT2 1 Rotor assembly 2 Source coil 3 Lighting coi I 4 Pan head screw 5 Spring washer 6 Timin...

Page 91: ...ad screw 13 Plug cop assembly 14 High tension cord 15 Spark plug 16 Main switch assembly 17 Pan head screw 18 Spring washer 19 Nut 20 Horn 21 Bolt 22 Spring washer 23 Stop switch assembly 24 Stop switch stay 25 Wire harness assembly 26 Connector cover 27 Connector cover 28 Handle switch 29 Pann eacl screw 30 Switch cord band 31 Handle switch holder 32 Handle switch 33 Pan head screw APPENDIX II JT...

Page 92: ...monthly or per mileage If hard usage clean and lube daily Do not over oil Use SAE 10W 30 SE PERIODIC MAINTENANCE INTERVALS 0 0 0 0 0 0 0 0 0 Initial Thereafter every Page Item Remarks miles miles 250 500 500 1 000 48 49 Brake System Complete A Chk Adj as required Repair as required 0 0 22 26 Clutch L Check Adjust as required 0 0 s 69 70 ISpark Plug 0 Inspect Clean or replace as required 0 0 0 46 5...

Page 93: ...assures is more than worth thP time involved orque Specifications The Iist below covers those stud bolt sizes with standard I S O pitch threads Torque specifications for components with thread pitches other than standard are given within the applicable chapter Torque specifications call for dry clean threads Components such as the cylinder or cylinder head should be at room temperature prior to to...

Page 94: ...nd re install spark plugs Kick engine over several times with ignition off to coat cylinder walls with oil 4 Remove drive chain Clean thoroughly with solvent and lubricate with graphite base chain lubricant Re install chain or store in a plastic bag tie to frame for safe keeping 5 Lubricate all control cables 6 Remove battery and charge Store in a dry place and re charge once a month Do not store ...

Page 95: ...0 762 1 016 1 270 1 524 1 778 0 1 2 540 2 794 3 048 3 302 3 556 3 810 4 064 4 318 0 2 5 080 5 334 5 588 5 842 6 096 6 350 I 6 604 6 858 I 0 3 7 620 7 874 8 128 8 382 i 8 636 8 890 9 144 9 398 0 4 10 160 10 414 10 668 10 922 11 176 11 430 11 684 11 938 I 0 5 12 700 12 954 13 208 13 462 13 716 13 970 i i 14 224 14 478 0 6 15 240 15 494 15 748 16 002 16 256 16 510 i 16 764 17 018 i I 0 7 17 780 18 03...

Page 96: ...rms m kg g kg km km I Meter Kilograms Usually torque Gram s Kilogram s 1 000 grams Kilometer s Liter s Kilometer s Per Liter Mileage Torque Weight Flow Distance Volume Capacity Misc Cubic Centimeter s cm3 Volume or Capacity Known ft lbs in lbs ft lbs in lbs lb oz mpg mph mi ft yd in in oz U S liq cu in pt U S liq qt U S liq gal U S liq lb in psi lb in 2 I Fahrenheit F cc kg mm kg cm2 Kilogram s Pe...

Page 97: ...il stop light Daytime charging circuit Night time charging circuit Battery circuit Ground circuit Front brake stop light circuit Rear brake stop light circuit Tail light circuit Head Meter light circuit Common circuit Head light mailT circuit Head light sub circuit Horn circuit Rectifier circuit G _ Green Red Red Black Green Y llow Yellow Blue Blue L Vf Brown Yellow Graen Pirnt v m ite _ ...

Page 98: ... ...

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