centre stand spring

It sounds like your spring is mounted correctly, so it's probably where the spring rotates.

You will find that where the spring is connected to the cross bolt it has worn a groove into the cross bolt, so try moving the spring a little to the left or right.  Alternatively, rotate the cross bolt a little if possible and grease up where the spring connects.

It could also be that the centre stand pivot is badly worn.  Jack the bike up, take off the spring and do a good inspection and I think you'll get it sorted.

Perhaps your spring is the wrong length or not strong enough.  Possibly it is a replacement that is not up to the job..... 

As Bob points out wear at either of the connection ends could be adding friction to the action. More greasing  of the spring end loops/hooks and stand bolts might help. You could try packing the top bolt and stand cross bar with sleeves made of steel to increase the spring tension.

Or do what I did years ago- use a bungee strap!

Signed, Bob the Bodger......

The centre stand spring + the connecting hook on my 650SS departed the machine whilst out riding a week or so ago. I have obtained replacement items from Andover-Norton (the spring being a larger diameter than the one it is going to replace). Does the open end of the connecting hook face forwards or rearwards?

I also had a centre stand spring break on my wideline dommi.  I obtained another stainless replacement spring, but decided not to fit this as I noticed a faint ring on the 90* radius near the hook.  The spring that broke was also stainless so I then fitted a non stainless spring which has now been on the bike for over 20 years.