G80 clutch centre binding

[AyJayBee]

I am rebuilding a 1960 G80 coil ignition, AMC box, but am having trouble when tightening up the clutch centre - it all just locks up and the centre will not turn, neither will the gearbox sprocket. There seems to be a spacer on the mainshaft, but it is set back compared to the inner chaincase. Should there be another or different spacer to overcome the 'lock up' (as opposed to 'lock down' -Boom-boom!). Any solutions appreciated. Ta. AB

[1608]

Its a common problem, I think you will find that after years of the hub centre being over tightened ( cos they do come loose) the stop ends on the hub splines
wear or become compressed. This causes the back of the splined hub to go too far back and susequently lock against the out-put shaft.If you look at the rear of the hub you will subsequently see a groove worn init from the out-put shaft. A quick fix would be to relieve that part of the hub,but a new replacement is the proper fix.
See my wobbly clutch hub mod in the tech articles.

[AyJayBee]

Checked the hub - there is a very slight mark on the back, but hardly noticable. Checking in the parts book there is a spacer shown - 040131 spacer for gearbox sprocket - which I do not think is there. The problem was discovered when I had to strip the rebuilt primary drive to fit the rear chain as I couldn't fit it with the primary drive in place. Turns out once the chain was on the gearbox sprocket and the clutch centre fitted it all went tight. Will this spacer overcome the problem?

[dave16mct]

040131 is the spacer between the gearbox bearing and the sprocket. The oilseal runs on it. I think what you can see behind the clutch is the projecting part of the sleeve gear.
Dave

[1608]

No, the hub is fitted the the input shaft. As the input shaft turns interdependently of the out put shaft the two shafts should not come into contact. As you tighten the hub centre nut it draws the hub up too tightly and then abuts the out put shaft.

[SPRIDDLER]

I am rebuilding a 1960 G80 coil ignition, AMC box, but am having trouble when tightening up the clutch centre -

It might help to get nearer to solving the issue to know if you have (or the PO has) ridden the bike as it was before you worked on the clutch/primary drive, or are you rebuilding a new-to-you or non-running project?
Have you replaced any parts when rebuilding the clutch?