First gear modification. In gear boxes made before number G8603 (250
c.c. model) and M2701 (350 c.c. model) a plain layshaft first gear 041291
was used. This is superseded by a bushed pinion 044080. The new first
gear can be used with the existing second gear pinion.
Wear on kickstarter axle bush. Only likely to occur on early models with
gear box numbers before G6014. This can happen if the kickstarter return
spring 040043 is overwound, which tends to pre-load the kickstarter
bush against the first gear pinion. Gear boxes after the above number are
fitted with a circlip 042900 encircling the kickstarter axle 042130 with a
thrust washer 042901 to prevent pre-loading also wear on the axle bush.
The new parts can be fitted to earlier type gear boxes.
Oil leaks. Two metal discs or core plugs are used to seal the aperture for
the layshaft and quadrant spindle. These discs are a press fit in the gear
box shell.
To rectify an oil leak from this part of the. gear box it is necessary to
take away the primary drive and rear portion of the front chaincase as
described in removing the engine. Take out the gear box internals to drive
out the discs and use replacements. Clean all traces of oil from the two
apertures, apply jointing compound and tap the new discs into position.
Allow plenty of time for the jointing compound to set before refilling
gear box with oil.
Oil leaks from end covers. Can only be due to a broken or deformed
gasket. Stick the gasket with jointing compound to the gear box shell
before refitting the cover.
Dismantling the gear box. (All nuts are right-hand, except rear chain
sprocket nut 041271.) With the gear box in the frame and clutch removed:
Remove exhaust pipe and silencer in one piece.
Remove right side footrest arm.
Remove gear indicator bolt 040137.
Remove gear change pedal, by releasing the pinch bolt.
Remove kickstarter crank bolt and nut, pull off the crank.
Remove four screws securing the fairing and take it away.
Gear box end cover. Take out the gear box drain plug, catch oil in a
suitable receptacle.
Remove ratchet nut 041340 and ratchet 041283.
Remove six screws securing end cover, take off cover then remove
ratchet and nut. The ratchet cannot be removed without taking off the
cover. See Fig. 3.
Gear box inner cover. Remove clutch inner cable from lever.
Remove, by unscrewing clutch body lock ring 041280, use a soft drift
and hammer.
Remove clutch operating body 042141 (watch for
a" ball inside).
Remove mainshaft nut 041265.
Remove ratchet nut 041340 and washer.
The cover can now be removed exposing internals,
Removing gear box internals. Remove footchange quadrant 041334 with
spindle assembled.
Remove, by unscrewing selector fork shaft 041345 (use a spanner on
the two flats).
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