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Tomos A31988 Workshop Manual

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Tomos A3 1988 Workshop Manual
The following is a modified and English-only version of the A3 manual found at www.classiccycles.org
Please note that this version is NOT guaranteed to be a perfect reproduction of the original; if you have
any doubts as to what you are reading, please check the original to be sure.
Technical Data ...........................................................................................................................................................2
Nuts, Bolts, and Torque Specs ...............................................................................................................................3
Special Tools...............................................................................................................................................................3
Image............................................................................................................................................................4
Engine Removal.........................................................................................................................................................5
Engine Disassembly..................................................................................................................................................8
Checking Engine Parts and Assemblies ..............................................................................................................11
Checking, Dismantling, and Assembling of the Clutch ....................................................................................13
Dismantling, Checking, and Assembling of the Countershaft ........................................................................15
Checking Pedal Shaft and Transmission Chain ..................................................................................................17
Carburetor Checking...............................................................................................................................................18
Encarwi Image...........................................................................................................................................18
Dellorto Image...........................................................................................................................................19
Reassembling the Engine .....................................................................................................................................20
Adjusting the Contact Gap and Ignition Advance ............................................................................................23
Oil Pump...................................................................................................................................................................24
Magneto Settings and Electrical Equipment.....................................................................................................25
Wiring Diagrams (COLOR!)
European without turn signals................................................................................................................26
European with turn signals......................................................................................................................27
U.S. without turn signals..........................................................................................................................28
U.S. with turn signals................................................................................................................................29
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  • Page 1: Table Of Contents

    Tomos A3 1988 Workshop Manual The following is a modified and English-only version of the A3 manual found at www.classiccycles.org Please note that this version is NOT guaranteed to be a perfect reproduction of the original; if you have any doubts as to what you are reading, please check the original to be sure.

  • Page 2: Technical Data

    TECHNICAL DATA Engine Single cylinder, two stroke, air cooled Bore x stroke 38 x 43 mm (1.496 x 1.693 in) Piston displacement 49 cm (2.990 in Compression ratio 8.5 : 1 Engine output 0.75 -1.5 KW Gear box automatic 2-steps, with two centrifugal clutches Ignition Flywheel magneto Ignition advance...

  • Page 3: Nuts, Bolts, And Torque Specs

    NUTS, BOLTS, AND TORQUE SPECIFICATIONS Part Thread Torque Spark plug M14 x 1.25 18Nm Cylinder cover 12Nm Flywheel 30Nm speed clutch M10 x 1 25Nm speed driven gear M14 x 1 80Nm Mainshaft chain sprocket 60Nm Cylinder stud bolts 15Nm Crankcase 10Nm LH engine cover...

  • Page 5: Engine Removal

    ENGINE REMOVAL Unscrew the footrest screw with 17mm wrench Drain the oil from the gearbox (fig 1) (fig 2) With 11mm wrench, unscrew the nut and drive For pedal versions, refer to figures 3a and 4a out lever pin (fig 3) Remove the hub, cups and springs (fig 4) Unscrew the three screws of LH and RH shield each and detach shields from frame (fig 5)
  • Page 6 Unscrew three screws of magneto cover and Remove the chain by removing master link (fig 7) detach cover (fig 6) For oil pump injection refer to chapter OIL PUMP Unscrew the crown nut and extract control cable Unscrew bottom screw on control cable cover and along with throttle piston (fig 8) release the spark plug cable (fig 9) Detach all electrical leads (fig 10)
  • Page 7 Unscrew all three engine screws with two 13mm Hold the engine by hand. Extract top screw (3) and wrenches (fig 12) remove the engine out of the frame (fig 13) Take the intake silencer out of the frame (fig 14)

  • Page 8: Engine Disassembly

    ENGINE DISASSEMBLY  Place the engine on the repair stand (special tool). Remove the carburetor and spark plug (fig 15) The pedal shaft and the countershaft are Detach clutch drum and sintered bush (fig 18) connected by a starter chain, so both shafts will have to be taken out together (fig 19) Rotate the engine placed on the stand so that the Remove the standard washers on the crankshaft...
  • Page 9 The flywheel is removed with the flywheel puller, Make a scriber mark across the bottom of the a 19mm, and a 32mm wrench (fig 22) stator plate and the crankcase in order to facilitate the re-timing. Remove the 3 screws and lift the stator assembly from the engine (fig 23) Slacken the chain sprocket nut.
  • Page 10 If the brass bushing in connecting rod needs to be Upon installing the new bushing, drill two replaced, use the connecting rod bush pulling key, lubrication holes according to the holes in the and replace with a new one using same tool connecting rod.

  • Page 11: Checking Engine Parts And Assemblies

    CHECKING ENGINE PARTS AND ASSEMBLIES Check both crankcase halves for possible damages or distortions, particularly the joint surfaces, to avoid later leaking of oil from the gearbox. Check all bearings. If clearance is noticed, the bearings must be replaced. Check the crankshaft between the center of a horizontal alignment tool and measure out-of-round on all the points indicated in figure 35.
  • Page 12 CYLINDER D (mm, in) 38.01 +0.01 (1.4964 +0.0024 38.02 +0.01 (1.4968 +0.0024 D > D max 0.012 mm Ma x permissible bore taper: 0.006mm PISTON 37.95 +0.01 37.91 +0.01 37.87 +0.01 37.85 +0.01 37.96 +0.01 37.92 +0.01 37.88 +0.01 37.86 +0.01 L = 50 mm L= 52.5 mm...

  • Page 13: Checking, Dismantling, And Assembling Of The Clutch

    CHECKING, DISMANTLING, AND ASSEMBLING OF THE CLUTCH Remove the circlip and separate the 1 and 2 Dismantle both clutches. The spring is removed speed clutches (fig 37) with a screwdriver (fig 38) In this manner, brake strips are released, and all Press pins out of shoes and check brake strips, three shoes can be removed (fig 39) spring inside of shoes and 2...
  • Page 14 Dismantling of the needle clutch is necessary only in case of replacement. A new needle clutch is pressed with special tool “roller clutch installer.” The needle clutch must be pushed with the signed side towards the center of the clutch drum, or else it may operate in the reverse direction (fig 43)

  • Page 15: Dismantling, Checking, And Assembling Of The Countershaft

    DISMANTLING, CHECKING, AND ASSEMBLING OF THE COUNTERSHAFT Fix the countershaft into a vice and unscrew the Remove the 2 speed gear (fig 45) nut with a 19mm wrench (fig 44) Remove the circlip at the shaft’s toothing (fig 46) Unfasten the wire spring and separate a small chain sprocket with roller cage (fig 47) Remove the 1 speed gear and shake the rollers...
  • Page 16 Reassemble the countershaft in reverse order of Put the chain sprocket in with cage so that the dismantling. beginning of the wire spring is turned 90 degrees left-ward from the spring nose (fig 49). Lock the Use of grease is not suggested because it may wire spring to riveted nose on the 1 speed gear impede the function of the self-locking clutch.

  • Page 17: Checking Pedal Shaft And Transmission Chain

    CHECKING PEDAL SHAFT (kickstart) AND TRANSMISSION CHAIN If it is necessary to replace the chain sprocket or claw collar on the pedal shaft or kick start, first rmove the protective ring (fig 50/1) and the spring washer (fig 50/2). During assembly, take care that the thinner part of the collar is mounted forward or else the brake spring will slide across the chain sprocket.

  • Page 18: Carburetor Checking

    CARBURETOR CHECKING Dismantle the carburetor into component parts (fig 52 Encarwi or 52a Dellorto). Clean the parts with carb cleaner and blow them out with compressed air. Check the parts. In case of wear throttle slide or leakage of float, replace with a new one. When reassembling the carburetor, take care that the float needle fits the float chamber cover.

  • Page 19: Dellorto Image

    FIGURE 52a – DELLORTO CARBURETOR...

  • Page 20: Reassembling The Engine

    REASSEMBLING THE ENGINE When reassembling the engine, replace all seals With the crankshaft bearings fitting tool, press the and gaskets. All parts of the engine should be crankshaft ball bearings into both crankcase halves thoroughly cleaned and lightly oiled. All gaskets (fig 53) should be given a light coat of grease to insure better fit and seal.
  • Page 21 Check that the crankshaft turns freely. Insert pedal The claw collar brake spring must seat in the shaft or kick shaft together with countershaft and recess in the RH half of the crankcase. Place chain (fig 57) washer 209.005 and bush 209.072 on the crankshaft (fig 58) Incorporate the clutch drum with mounted 2 Handle the roller clutch carefully and if it is...
  • Page 22 Before securing the nut with washer, it is necessary to check the proper function of the assembly. Firmly hold the 2 speed driven gear with the left hand and the clutch drum with the right hand. When the clutch drum rotates counterclockwise, both clutches idle.

  • Page 23: Adjusting The Contact Gap And Ignition Advance

    ADJUSTING THE CONTATCT GAP AND IGNITION ADVANCE These two operations are interrelated and proceed as follows. -Screw the dial gauge support tool and the dial gauge into the spark plug hole. -By rotating the flywheel, put the piston at TDC and set the dial gauge to zero. -The breaker points are fully open at TDC.

  • Page 24: Oil Pump

    OIL PUMP After assembly or repair of models with oil pump, you must keep to the following instructions The pump is connected to the magneto nut on the Unscrew the bleed screw on the oil pump and wait crankshaft by a special clutch (fig 68) until oil from the tank under the seat flows to the pump.

  • Page 25: Magneto Settings And Electrical Equipment

    MAGNETO SETTINGS AND ELECTRICAL EQUIPMENT The voltage regulator should be checked when bulbs blow frequently. During the check, the engine should be operating and the lights switched off-on, alternatively. The voltage should always read 12+/- 0.5 V. Before replacing the regulator, make sure the improper operation is not due to bad grounds. The direction indicator relay should be checked within the wiring system.
  • Page 30 Brown Yellow Black Brown...
  • Page 31 MOTORCYCLE PARTS & ACCESSORIES Click on links below Tomos Motorcycle History & Technical Specifications Motorcycle Parts & Accessories Dirt Bike Parts & Accessories Harley Davidson Parts & Accessories Motorcycle Helmet Closeout Sale Japanese Motorcycle Original Equipment Parts Save On All Motorcycle Tires...

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