Suzuki Across problem

[GoneRiddin]

Hi all, I am currently restoring a GSX-250f Across and have run into a problem. I'm hoping someone can shed some light on it for me.

I bought some sprockets and a new chain, shortened the chain to 110 links no problem.
I came to fit the new drive sprocket and found that the shaft seems worn.
When the old sprocket or the new one are slipped onto the splined shaft. They are nice and snug on the outside, before where the circlip goes, but when the sprocket is slipped onto the home position, there is some rotational movement of the sprocket to the shaft.

My question is, Is the drive shaft difficult to replace and what amount of wear is acceptable if any. In my mind the shaft should be the same from outside edge right down to the collar on the inside.

Any comments on this would be much appreciated

[Nero Diablo]

Might be worth posting this is the technical section instead of the hi how you doing section. There are various links to workshop manuals available but generally the output shaft is a split the cases pull the gearbox apart.