Removal of gearbox sprocket

[bevanclark]

Hi folks,
The driving sprocket on the G107 gearbox on my VB is quite worn, so I was considering replacing it whilst I had the primary side off. Simple question is: how do I get it off ? Having undone the nut, I find that it cannot clear the shoulder on the mainshaft - see attached image - is this normal ? I expected it to be very similar to my Panther's BAP box, in that you just withdraw the nut, then the sprocket; but it seems not. Surely I don't have to dismantle the entire box so I can withdraw the mainshaft out the clutch side, in order to get the driving sprocket off ? It seems from Waller, that this may be the case, but I'm hoping not.
Puzzled,
Bevan

[adrie.degraaff]

Surely I don't have to dismantle the entire box so I can withdraw the mainshaft out the clutch side

Yes, but just the deck so you can undo the nut, slide a fitting-rod in to it's place when taking the mainshaft out so the sprockets stay in place.

[bevanclark]

Thanks Adrie; what a pain, just to change the sprocket. The gearbox is very smooth and quiet, so I'm not keen to disturb it; I'll see if I can do as you have suggested. Cheers, Bevan.

[adrie.degraaff]

what a pain, just to change the sprocket.

Only ones in a lifetime.

[david.anderson]

It is possible to slide the mainshaft out. But you must first remove the gearbox outer cover, partly dismantle the kickstart assembly and gearchange then remove the mainshaft nut. If lucky the mainshaft will slide back in with a little jiggling. Be careful to align the gearchange timing marks on reassembly. It is probably easier however to completely dismantle the gearbox, being careful not to lose the loose rollers on dismantling.
David

[bevanclark]

Thanks David,
Inspection of the rear sprocket suggests that it is also quite worn, so I'll put things back together for the time being, while I try to get new ones so I can replace both at the same time. At least I don't have to take the engine out first, as you do with the Panther !
Cheers, Bevan