Removing sprocket bearing

I have a 78kz650b 29000 miles which the bearing on the sprocket shaft blew apart while riding it and jammed the shifting mechanism at 30 mph and locked the rear tire. i was wondering if this has happened to anyone else, luckily i had a spare motor, can the bearing be accessed from the bottom of the motor without taking the cylinder and heads apart. This motor ran awesome thats why i don't want to disturb anything.




78 kz 650b
78 kz 650 sr
79 kz 650 sr big bore turbo

can the bearing be accessed from the bottom of the motor without taking the cylinder and heads apart.

To access/change the bearing you need to remove the lower crankcase as the bearing sits between the case halves, and yes, this can be done without disassembling the topend.

Removing the lower case requires you to remove all engine side covers (clutch, points, alternator, sprocket and transmission cover) and the starter motor. Then you have to remove the clutch, clutch basket and hub, oil filter, oil pan, oil pump, secondary shaft and starter clutch assy.

Remove the casing bolts (13) from the top, flip the engine over upside down, remove the casing bolts (six 6mm and ten 8mm) from the bottom and remove the lower case. The shift drum, shift forks and kickstart mech. all come off with the lower case, leaving you access to the transmission. Obviously you should leave the engine upside down until the lower case is reinstalled.

I have lots of pics of the process, let me know if you need any - here´s one with the lower case removed.

Oops, pic didn´t attach, once more: