Not sure if you have the same kind of sprocket retainer as a 900, but you probably know that the 2000 M900ie has a unique sprocket for that year. It has bosses on both sides and I believe it sits 5mm further inboard than the other 900s.
I couldn't get the right sprocket for mine when I last changed sprox and chain, so I made a 5mm spacer for a standard sprocket and it works fine.
It was simple to make by just cutting a ring out of 5mm ally sheet with two hole saws of appropriate size . I used 5mm longer screws too.
Sounds like there is a spacer stopping your sprocket from moving closer to the engine?
Do you mean the boss on the sprocket?
I still have the proper y2000 worn sprocket somewhere if you'd like me to measure it... They are available, I was just lazy!
