A Group Models (Without Swinging Arm Frame)

Clutch Adjustment

Fig.25. Clutch control adjustment

Two adjustments are provided at the clutch control arm on the gearbox outer cover. The first of these is at the clutch push rod and is exposed when the inspection plate (Fig. A25) is removed. It consists of a grub screw and lock nut Between the inner end of the screw and the clutch push rod a steel ball is inserted, and the grub screw must be adjusted so that there is just a little clear­ance between the ball and push rod.

To carry out this adjustment loosen the lock nut A and with the aid of a screwdriver adjust the grub screw B. Then re-tighten the lock-nut

The other adjustment, to be used only if necessary, is provided by the cable adjuster on top of the gearbox, just under the magneto. Remember, however, that some free movement in the control arm is necessary, as if the adjustment is too tight there will be constant pressure on the clutch, with consequent wear and, loss of efficiency.


Clutch Spring Pressure

Fig.26 Clutch spring adjustment

After a considerable mileage it may be desirable to increase the spring pressure a little. First remove the outer half of the primary chaincase and then the domed clutch cover A (Fig. A26). which is secured to the clutch body by twelve screws. It will then be seen that the clutch plates are pressed to­gether by springs, the tension of which is controlled by the nuts B. To increase the spring pressure tighten these nuts B a few tarns. It is important that each of the six adjusting nuts be given an equal number of turns to ensure even pressure; otherwise the plates win slide unevenly and clutch drag may result After adjustment, replace the cover and chaincase.



Rear Chain Adjustment (Rigid Frame)

The rear chain is adjusted by means of screw adjusters in the fork ends in front of the wheel spindle. Slacken off nut A (Fig. A29) and then unscrew the spindle a little by means of a tommy bar inserted in the note in the spindle end B. Screw the adjusters C in or out until the chain tension is correct, with an up and down movement of three quarters of an inch. Make sure that the wheel is hard up against the adjusters when checking and also that the adjustment is equal on both sides of the wheel, so that the latter is in correct alignment in the frame. This can be done either by glancing along the line of both wheels when the front wheel is set straight, or by means of a long straight-edge, or the edge of a plank placed along the sides of the wheels. The straight-edge should touch both walls of both tyres, if the tyres are of the same section.

For rear chain adjustment on spring frame models see Chapter 13.

NOTE. It may be necessary to re-adjust the rear brake, since this will have been altered by movement of the rear wheel.






Front Chain Adjustment

 To adjust the front chain, remove the inspection plate plug A (Fig. A27) and then slacken off locknut B on the chain tensioner adjuster. Turn the adjuster C, screwing it up to reduce the slack in the chain, and down to increase it Feel the tension by inserting the fingers through the inspection plug hole. The correct amount of slack, or up and down movement, on the front chain is half an inch. If the play is being increased. pressure on the kick starter will help to move the tensioner plate down. This is of course unnecessary when play is being reduced.


Fig.A30. Exploded view of the clutch




Dismantling and Reassembling the Clutch

 A Group (Except Swinging Arm Models)

Take off the near side footrest, and then undo all the screws round the rim of the chaincase, noting the position of the red screw, which also serves as an oil-level plug. The joint washer should be carefully preserved.

The clutch is revealed by removal of the cover held in position by twelve nuts and bolts. Take care not to damage the oil sealing washer between the cover and the clutch body, when the clutch cover is drawn off.

The clutch spring plate which is now revealed may be removed after the six adjusting nuts have been unscrewed and the clutch springs and spring cups withdrawn.

The clutch plates may now be withdrawn. Take note of their position so that they may be re-assembled in the same order. Examine the clutch plates for oil or wear. The plates will require a thorough washing in petrol if there is any trace of oil on them. If the inserts are badly worn or glazed they must be renewed. The steel plates should be smooth and if badly scored they must be replaced.

Removal of the clutch body entails removal of the engine shaft shock absorber and sprocket, and the operation is described fully in Chapter 6.

The clutch sprocket and clutch centre can then be examined for wear. Special attention should be paid to the slots in which the steel plates slide; if any grooves or notches are worn in the sides of these, they may be filed smooth if not too deep. If the sprocket teeth are worn to a hook shape, the sprocket roust be replaced; otherwise rapid chain wear will result. Finally, examine the rollers and tracks. If wear on the chainwheel bush or on the bearing boss of the clutch centre exceeds .0015 in. the bush or centre should be replaced.

Re-assembly of the clutch and mainshaft sprocket is described in Chapter 8 Reference to Fig. A.30 and Fig. A.23, Chapter 8. will show the order and method of assembly.

It is important that the pressure plate and clutch plates should slide out evenly when the clutch is operated, and if necessary the clutch springs should be adjusted to achieve even pressure all round.




Chain alterations and repairs

 - All Models

A chain rarely breaks if it is kept properly lubricated and adjusted. Usually it is worn out long before it reaches breaking point. The rear chain is the most heavily stressed and is therefore the one most likely to give trouble. Spare parts should be carried to enable the rider to carry out a repair on the road with the aid of a chain rivet extractor (see Fig. X7). The front chain will probably be worn out before it requires shortening.




How to use the chain rivet extractor

First press down lever A (Fig. X7) to open the two jaws B. Insert the link to be removed so that the jaws grip the roller and support the uppermost inner side plate. The punch C is then screwed down on to the rivet head until the rivet is forced through the outer plate.




To shorten a worn rear chain

After a big mileage, the rear chain may have stretched so that no further adjustment is possible by the usual method. In this case it is possible to shorten the chain by one link or pitch, so increasing its useful life. First remove the single connecting spring link A securing the two ends of the chain (Fig. X8). If the chain terminates in two ordinary links as in Fig. X8 (in which case the chain will be of an even number of pitches) extract the third and fourth rivets B from the end and replace the detached three pitches by a single connecting link Q. The connection is made with an additional spring link D. If one end of the chain has a double cranked link (Fig. X9)—in which case the chain will have an odd number of pitches—extract the second and third rivets A, releasing the cranked link unit complete, which can be retained for further use. Replace with one inner link B and again connect up with an additional single connecting link C.








To repair a damaged chain

If a roller or link has been damaged (X, Fig. X9) remove rivets D. take out the damaged link and replace with one inner link. secured by two single connecting links.

It is important that the spring clip fastener should always be put on so that the CLOSED end faces the direction of travel of the chain—i.e., when clip is on top run of chain, closed end is toward front of machine—when clip is on bottom run, closed end is towards rear of machine.

It should be noted that once a rivet has been extracted it must not be used again, so that it is important to check that the correct rivet is being removed before actually removing it. In the case of double cranked links, the complete unit comprises an inner link and the cranked outer link—three rollers in all—and these must never be separated.




Fitting rear chain

To fit a new rear chain, turn wheel until the spring link of the old chain is located on rear sprocket. Disconnect, and allow the lower run to drop down. Join the top run of the old chain to the new chain by means of the connecting link, and then by pulling on the bottom run of the old chain the new one will be carried round gearbox sprocket. Then the old chain can be disconnected and the ends of the new one joined together.

When the rear chain breaks and falls from its sprockets, the new or repaired chain can be replaced without taking off the chainguards. One end of the chain must be fed (from the rear) under the front end of the rear top chainguard on to the gearbox sprocket. A long bladed screwdriver or a piece of stiff wire may assist this operation. When the chain has located on the sprocket teeth, engage a gear and gently turn gearbox over with the kick-starter. This will feed chain round gearbox sprocket. When sufficient length of chain is hanging below sprocket, disengage gear and chain can then be pulled round until both runs can be fed inside rear chainguard and engaged on rear wheel sprocket.