I'm assuming the 600 uses the same 'snow mobile' type that the other models use?
If so this is what you want:
https://www.catalyst-findit.co.uk/in...64&pid=MK-DF62
Obviously worth looking around at the vacuum pipes that drive the diaphragms to ensure there are no cracks or splits etc. and also if your bike has a vacuum fuel tap check that is working correctly too. Unfortunately there's no rebuild kit available for that one and it's about £30 from Moto Rapido with club discount.