Index of page contents (quick links) Engine unit reassembly Refitting the crankshaft Fitting the piston, cylinder, etc. Fitting engine unit into frame ENGINE UNIT REASSEMBLY Reassembly of gears: fit the layshaft ball bearing by warming the case first, and fit the oil seal with the spring side toward the bearing. Now fit the square retaining plate, noting that the recess in the plate goes toward the bearing, tighten the four nuts and bend over the locking tabs. Now slide the cursor sleeve onto the layshaft, taking care that the two balls with the spring between them are properly housed in their transverse hole; the sleeve retains them when slid right home. Now on the smaller diameter of the layshaft, assemble first the spacer and then the dished washer. Now insert the shaft from inside the box, making sure that the loose pad on the end of the selector arm enters the annular groove on the cursor sleeve. As the shaft is pushed home it may need to be tapped lightly with a copper hammer to seal it in the bearing. Now slip a suitable tubular distance piece, and the washer and hub nut, onto the shaft. Tighten the nut lightly, just sufficient to compress the rubber sealing ring. If the mainshaft bearing was removed, replace the shim, and then drive the outer track into it's recess in the casing. Place the spacing washer on the short end of the mainshaft, put the needle rollers into the outer track, and enter the shaft into the bearing. Now assemble the gears on the layshaft. If the gears have been kept together, there will be no difficulty. If they have been seperated, or new ones are being fitted, start with the top gear wheel - this is the smallest, and the raised collar on the inner diameter should face to the offside. Check that it's front face is flush with the front face of the gear it meshes with. Second gear should be assembled with the innocenti marking to the offside - some gears have no marking, in which case it may be assumed that the two sides are symetrical and identical. First gear should have the kickstarter ratchet teeth facing to the offside. Check that all the gear wheels are flush with the gears on the mainshaft cluster, and that they spin freely. Place the large, thick shim washer in it's recess in the first gear wheel and then the smaller washer. Before assembling the needle roller bearing and the ball bearing into the gearbox endplate, check that the two dowel pins are not burred or distorted. Fit the bearings to the plate and fit it over the four studs, making sure that the dowels go into their holes squarely. The plate may need light tapping to seat it; put on the four washers and nuts and tighten them. Ensure that the whole gear assembly is free to turn with the endplate in position. Measure the gap between the inner face of the endplate and the large shim washer with a feeler gauge. Minimum gap should be 0.003in and maximum 0.011in. If not within these limits, the tolerance must be adjusted by fitting a different large shim washer of the required thickness. If the clearance is correct, the hub nut and distance piece may be removed - the purpose in fitting them was to compress the rubber seal behind the layshaft bearing, which otherwise would take up the desired endplay. Assembling the clutch: on the clutch shaft (which protrudes through the endplate) put first the small washer then the larger one. Fit the needle roller bearing to the clutch body; place the chain on the sprocket teeth, and fit the body to the shaft. Fit the inner clutch bell, put on the lock washer and nut. Use tool 70644 to hold the bell and tighten the nut. Knock over the lock washer. If the engine unit is in the frame: next place the engine sprocket in the loop of the chain and slide it on to the splined sleeve. Fit the sliding dog, spring and spring collar in that order. Now screw in the bolt using tool 70644 to prevent the socket from rotating. Do not screw the bolt right home until the collar has registered properly with the splines - take care to ensure this is so. Once the collar is registered, tighten the bolt and remove 70644. Now fit the clutch pressure plate and insert the five springs, tilting the plate to get the springs into their proper position. (If the unit is out of the frame, this is more easily done by laying the unit on it's side, clutch uppermost). Place the six clutch plates in their correct order ( a friction plate first, a plain plate last ) against the pressure plate, and fit tool 70643. Compress the springs and feed the clutch plates into their grooves. Latsly fit the circlip, making sure it's end comes over a projection of the clutch bell, not over a gap. When the circlip is seated propely, remove 70643. Complete assembly as follows: Fit the chain tensioner plates - the smaller (lower) plate goes underneath the larger one. Fit the two securing screws with their washers, run up finger tight, and adjust the larger plate until the chain has 3/8 in. up and down movement in the lower run at it;s tightest point. Then tighten the two screws. Check the condition of the gear cover hallite gasket, and fit the gear cover, make sure the short clutch pushrod is in position and does not drop out as the cover is seated on it's studs. To check this, press the case hard with one hand, moving the clutch operating arm with the other. If the pushrod is in position there will be about a quarter of an inch free movement only of the arm. Fit the silencer support bracket on the forward stud, and the brake cable clip on the next lower stud. Position the exhaust pipe clip on the stud just below the kickstarter. Fit the twelve washers and nuts, and tighten. Fit the stud securing the silencer to it's bracket and tighten. If the engine unit is out of the frame: the next operation after completing the clutch assembly, is to refit the crankshaft. Back to Index REFITTING THE CRANKSHAFT Before commencing assembly, note that new oil seals must be fitted throughout every time the crankshaft is removed and replaced. Turn the engine unit over, magneto side uppermost and fit the offside ball bearing into it's housing. Put over it the Hallite washer. Check that the circular plate is flat and has not been distorted by uneven tightening of the screws. If in order, fit the oils seal to it, with the spring facing in towards the crankcase centre. Now fit the three screws, tighten evenly, and lock them with a centre punch on the edge of the heads. Fit the crankshaft into place from the magneto (near) side, and rotate it as it enters the oil seal to prevent distortion. Once past the seal, it will need to be tapped home into the bearing with a hide mallet. Reassemble the near (magneto) side bearing. Fit the small oil seal into the housing spring inwards, then the spacer washer and the roller bearing track. Fit the large oil seal with the spring facing outwards (towards the crankcase centre). Pack the needle roller bearing with a medium grease. Check the Hallite gasket for condition, and fit the bearing housing; a smear of grease on the large oil seal will assist it to slide over the shaft. As the housing is tapped home check that the crankshaft is free to rotate. Make sure the groove at the top of the housing comes opposite the hole for the electric leads. Fit the three washers and nuts and tighten evenly. Fitting flywheel, magneto and timing the ignition: first fit the woodruff key for the flywheel to it's keyway - make sure it is a firm fit, or it may be dislodged as the flywheel is fitted. Now thread the electrical leads, in the black sheath through the hole in the crankcase. Fit the stator, ensuring registration of the marks made before dismantling. Fit the three washers and Phillips screws and tighten. Now fit the flywheel on to it's taper, making sure the key is not dislodged. Fit the spring washer and then the retaining nut (this nut has a left-hand thread). Tighten to 25lb with a torque wrench, using tool 70648 to hold the crankshaft. The timing is correct if the contact points are just breaking when the arrow on the flywheel rim is opposite the notch on the housing. (22 degrees before TDC). If the points are found to be just not breaking, slacken the three Phillips screws and move the stator, backwards or forwards, to obtain the desired result. The moment of the points breaking can be checked as follows - obtain a bulb holder with two leads attached, and a headlamp bulb. Take one lead to battery positive and connect the other to the green ignition lead coming from the magneto. Now earth the battery negative with a third lead to the crankcase housing, and the bulb will light. Turning the flywheel will make the bulb dim as the points open. If at this point the arrow and notch are not registering, move the stator as described above. Fitting engine-shaft shock absorber: fit the dished oil thrower to the offside crankshaft, the dish facing outwards, and then fit the long splined sleeve. Put the engine sprocket in the loop of the chain and slide it on to the splined sleeve with the dogs facing outwards. Fit the sliding dog, spring and spring collar in that order. Now screw in the bolt, tool 70648 will prevent the crankshaft from turning. Do not screw the stud right home until the spring collar has registered properly with the splines - take care to ensure this is so. Once the collar is registered, tighten the stud, and remove tool 70648. Fit the chain tensioner plates - the smaller (lower) one goes underneath the larger one. Fit the two securing studs with their washers, run up finger tight, and adjust the larger plate until the chain has 3/8in up and down movement in the lower run at it's tighest point. Then tighten the two screws. Check the condition of the gear cover Hallite gasket, and fit the gear cover, making sure the short clutch pushrod is in position and does not drop out as the cover is seated on it's studs. To check this, press the case hard with one hand, moving the clutch operating arm with the other. If the pushrod is in position, there will be about 1/4in free movement only of the arm. Fit the brake cable clip on the first forward lower stud, and then fit the twelve washers and nuts. Tighten all of them except the two, at front and back, which secure the silencer and exhaust pipe brackets. Fill the gearcase with its oil - 3/4pint of SAE 90. (Note. This can be done before fitting the gear cover, provided the unit is laid on it's side with the transmission uppermost. This saves the time involved in pouring the oil through the comparatively small filler-plug. But care must be taken to keep the unit in position until the cover is fitted, otherwise some very messy spillage will result). Back to Index

FITTING THE PISTON, CYLINDER, etc. First on the nearside, fit the waterproofing assembly to the generator leads - this will keep them out of the way when working on the piston, etc. later. The assembly comprises, in this order, a gasket, a flange plate (dish downwards), a grommet and a second flange plate (dish upwards). Feed the sheathed leads through these parts in turn - care is needed not to ruckle the sheath, and a light smear of grease helps. Secure the assembly to the crankcase with the two screws. Next fit the roller bearing in the small end eye, and fit one new circlip to the piston. The piston may need to be heated, to allow the gudgeon pin to be fitted easily. Take great care when pushing the gudgeon pin home, to avoid damaging or dislodging the roller bearing. Once it is home, fit the second circlip. Note that it is useful, whilst fitting the piston, to grip one forward lug of the crankcase in a vice, with the back of the unit resting on the bench. Also, an alternative method of fitting the gudgeon pin, is to use an old one, reduced a few thou., by polishing, as a guide to line up the piston and the little end - if this is done, both circlips are fitted after the gudgeon pin. Check that the piston has been fitted correctly with the arrow on the crown pointing toward the exhaust. Check the piston ring gaps before fitting. If any of the old ones exceed 0.025in gap, they should be discarded, and new rings must have gaps adjusted by careful filing to 0.008in. If any of the old rings are to be used, make sure they go back into the groove in which they were fitted. Fit a new cylinder base gasket, and slide on the barrel, taking care that the rings are not damaged. Fit the head gasket (the old one may be used if in good condition) and the head. Fit the four washers and nuts, the long nut goes on the front offside stud. Tighten down evenly, a little at a time. Fit a new exhaust pipe gasket, then the pipe and the two washers and nuts, but leave them finger tight until the silencer and exhaust pipe brackets have been fitted to the gear cover studs. When the exhaust system has been settled into place, tighten up all the nuts which retain it. Fit the cylinder cowling, held by two screws into the flywheel housing and one into the extended cylinder head nut. Fit the sparking plug. Fit the flywheel cover - it is held by five screws, and the top right hand may be left finger tight until the unit is back in the frame, when the earth lead is fixed under this screw. Fit the rear brake cable, if this was removed. There is a shouldered collar (ferrule) which forms the stop for the outer cable. The end of the inner wire is looped round the clamping stud which fastens it to the long adjusting screw, and the end must be brought back alongside the cable, and gripped by the two earsof the clamping plate, when the stud is tightened. Back to Index FITTING ENGINE UNIT INTO FRAME Position the unit below the frame and raise the rear end with a block of wood. Fit the rear spring bottom bolt throught the holes in the casing, and run the nut up but not tight. Fit the lower end of the damper to it's lug, fit the stud but do not tighten the nut completely. At the front, fit the pivot cones into the lugs (a smear of grease will help to retain them) and fit the distance piece between the lugs. Now lift the front end of the unit and place a block of wood under it. Use an old pivot spindle, or other suitable rod, as a mandrel to align the crankcase lugs with the pivot bearing. Smear the pivot bolt with grease, and run back the nut which was left on, on removal, to the end of the thread ( the old tab washer may be used again). Enter the bolt through the pivot bearing, and tap gently home using a hide mallet on the nut run back, making sure that the lugs stay in alignment with the frame bearings as this is done. When nearly home, turn the run-back nut down a few threads, till a flat coincides with the tub washer, and tap finally home. Put on a new tab washer and the nut on the other side, tighten up and knock over the tab. (Note it may help during this operation to loosen one or both of the bearing flanges, which are secured to the frame by four studs. This should not be necessary, but if it is done, make sure to retighten all the screws) Now lift the back of the unit and insert the auxilliary stand. Next tighten the nut on the end of the stud securing the lower end of the damper. Check that the shoulder, on the underside of the bottom plate of the rear spring, is fitting snugly against the outside edge of the casing, and tighten the nut securing the spring. Fit the rear brake cable into it's clip under the unit, and fit the shouldered collar (ferrule), which forms the stop , into its hole in the channel under the footboard. Scribe a line on the end of the pinch-bolt to show the direction of the transverse hole. Fit the rubber gaiter to the free end of the inner wire, after it has been brought through the stop. Now enter the pinchbolt into the two links and enter the wire through the hole in the pinchbolt, using the scribed line as a guide. Grip the end of the wire with pliers, pull tight and bend downwards while the washer and nut are put on the pinchbolt. Tighten this nut finally using two spanners, one on the head of the bolt to prevent it turning and distorting the wire. Refitting clutch and gear control cables:Refit to the top of the crankcase the bracket which forms the stop for gearchange and clutch cables - there is a gasket under the bracket, and note that a washer fits between the bracket and the swivelling lever. Tighten the two securing bolts. Refit the gear control tie rod (flat strip) to the selector lever and secure it with it's washer and circlip. Before fitting the clutch cable: note that in the trunnion which forms the nipple for this and the gearchange cables, there is a small disc below the central nipple-screw. This loose disc prevents the screw cutting into the wire when it is tightened. To fit the clutch cable, slide the trunnion off it, and pass it through the central adjuster on the gearbox bracket. Now unscrew the nipple-screw, and tap the trunnion on the bench, to shake out the disc. Now drop the trunnion through the end of the clutch operation lever, pass the cable through the transverse hole, drop in the disc and then run the nipple-screw down finger tight. Hold the trunnion body with a spanner whilst the nipple-screw is tightened. Finally, adjust the cable so that there is 1/16 in free movement at the handlebar lever. Now refit the carburetter to the induction stub, and turn the clamp so that the nut is at the top before tightening - this will allow maximum spanner room. Fit the carburetter cable, and push the flexible pipe onto the float chamber union. Refit the choke control into the carburetter, and check that there is a little free play in the operating cable. Refit the rubber hose connecting the air cleaner to the carburetter, check that it is not chafed or broken - airleaks will upset the slow running. Fit the upper circular clamp with the screw underneath, so that it does not chafe the ignition lead. Refit the latter lead to the sparking plug. This completes work on the offside of the machine. On the nearside, refit the brake shoes, if these were removed, to lubricate the cam spindle. Refit the rear hub, making sure the split cone is on the spindle first. After the hub, fit a new tab washer, and run the nut up finger tight. To hold the hub whilst tightening depress the brake pedal and jam a hammer shaft between the pedal and the underside of the footboard. Now tighten the hub nut to 65lb with a torque wrench, and bend over the tab washer. Replace the back wheel. Refit the generator leads - first they must be eased through the rubber cover, this must be done carefully. Plug the leads into the appropriate sockets in the junction box according to their colour, and refit the rubber waterproof cap. Refix the earth lead under the top screw of the flywheel cover and refit both sidepanels. Back to Index