If you need to tune your carbs and or syncing them you will need an Auxiliary fuel tank.I made mine out of an old Petrol/Gas treatment bottle.They have a teat on the top so it's easy to put a bit of fuel pipe on.The Small rubber patch was super glued on and drilled as a seal for the small Self tapping screw.This stops the bottle leaking when you fill it and then can be removed when upturned so there's no vacuum caused to stop the fuel flowing
On the CXs there's the rear engine hanger in the way but I usually take that off whilst I do them as it makes it easier to access the sync screw.
Tip:If when you tighten the small 8mm M6 locking nut the carbs go out allow for this by having the carbs slightly uneven so the nut brings then in when tightened