I have just bought a 67 shovel that has been stored for a while. With the engine not running I can change gear and get her in neutral easily, crisp and simple.  Once started it is a bugger to get into neutral and to move through the gears when stationary with the clutch lever pulled in.

I just need a couple of starting points so that I can eliminate some of the potential issues before I start trying to fix the problem.

Any advice would be gratefully received. Thanks !

Whats the change like while riding?

Clutch issues with a shovel??? no way haha

you will have to clean the clutch plates  the fibres & the steels  & then readjust the clutch , make sure you have full lever travel, e.g. thicker hand grip's aftermarket shitty clutchlever perch etc all reduce clutch action

if it has the one piece primary cover as dave sias remove it, if it has been changed out for a later cover with inspection remove the whole cover any way for better access, read through your clymer ...after you've removed all the plates you have a 3 or 5 finger clutch hub,, dont worry about a bit of wear on the fingers but you want the threaded fingers to be tight in place.ive seen these installed were the installer didnt know what the 3 or5 small springs were for & left them out,
they hold the clutch drum in place if these arnt working right you will have bad clutch, also if you remove the clutch hub its left hand thread, & be carful of the locking tab holding it ,save it & re use if you dont damge it.Also you should purchase some of these because you will need em one day..if its a standard set up & you have a lot of small rollers in a cage.(bearing retainer)think about the kit that does away with all that, l forget what there called now they use long needle rollers & work very well over the std stuff.cheap too.they also need to run wet,(plates & friction) to work correctly,, so after you have cleaned every thing up oil it ....