I used to use a Premier drumstick through the small end eye to tighten up the alternator nut. Drumsticks are made of very hard wood but not hard enough to damage anything. Over time the drumstick got chewed up so I bought a tool from Rex Caunt - happy days - now I never have clutch locking and nut tightening problems again.  

As an aside: I have been horrified to see people putting a tommy bar through the small end eye and letting it bear directly against the crankcase faces. The end result is damage - even if you cannot see it - these crankcase faces will leak air and cause incessant problems and teh small end bearing will get crushed and need replacement.  However, all is not lost - SRM in Aberystwyth can re build and re-face your crankcase mouth - its not cheap but it is possible and fitting a new roller bearing is not too difficult.  However you need to strip the whole engine down to bare cases to get this done at SRM and you need to get your cases to West Wales. 

The Rex Caunt tool is the best way forward - especially if you plan to do a fair bit of work on the 4 speed bikes.     

Rex has a double ended locking spanner which is very useful.

i am always wary about locking the engine with a bar through the little end. If you do use that method put some wood on the crankcase face.

i have used an impact wrench to lock the alternator nut. This is the way a lot of dealers do it. Don’t sack the torque up too high!

for the gearbox sprocket, it needs to be tight to stop it chattering on the splines and wearing the sprocket teeth 

( DAMHIK). You can wedge a lump of lead between the sprocket and the casing and the teeth will lock into the lead and you can then tighten the nut.