Before you dive in, check out the new and exchange carb service i offer in my ebay shop . there are about 20 things to check/set and replace I havent shown here as they are too difficult for the enthusiast. Go to the Vire 7 carb page for more details

Above: stripped and complete carbs

Before stripping, you can check the fuel pump diagragm hasnt ruptured

suck on the pipe going from the crankcase - there should be a resistance, if you can suck air thru - the diapragm must be broken/leaking.

another check is to make sure jets and galleries are clear

before removing low (idle-screw) and high (power-Tbar) speed jets from the side, it is worth noting how many turns out they have been adjusted to (count the turns to the nearest eight'h of a turn until the jet GENTLY comes to a stop. noting the turns for each Usually it is 1 turn out +/- 0.5 turn.

place a bowl/tray to catch the petrol, remove the two jets.

remove the HT cap to prevent firing, and run the engine - this will eject/clear debris from the galleries, and give you an indication of the fuel supply, and contamination if any. you can also inset a piece of 1/4" (like used in windscreen washer) tube into the jet and blow out any grit?

it might be possible to make a wire tool to clean out the bleed holes, but id advise removing/stripping instead

you can't clean out the mixing chamber unless you drill/pry out the welch plug and replace with a new one.

replace the jets, resetting them to the original turns-out, or 1+1/4 turns out if you forgot.

if the crank case pipe is not connected it wont pump fuel

if the carb is flooding/leaking fuel - suspect the float-diapragm is compromised/leaking