The Moto-Guzzi Nuovo Falcone VOC

Option 1; remove the flywheel (need special tool)
Option 2: remove rear engine mounting, and jack up the engine until there's enough room to take it off. I did that to change the spring, as I couldn't get the flywheel off! There's a link somewhere; probably in the Friday technical section

Hmmm. Yes, I think I've misunderstood the question.
Try this: http://nuovofalcone.createaforum.com/engine-and-transmission/gearbox-sprocket-replacement/msg1303/#msg1303