Carburetors leaking petrol

Started bike up this morning (first time in a few months) and found the back carburetor was leaking petrol. Called in at my nearest garage and the mechanic suggested dirt in carburetor preventing it closing properly and flooding it, said I just needed to clean out the dirt preventing the pin from coming down.

He helped me take the tank off and carburetor out, clean it and put it back on the bike. All proved very finicky (particularly putting the airbox back on), when the bike restarted engine kept cutting out as soon as the throttle was released. Mechanic said just needed petrol pulling through and would be fine, it would cure itself riding home. Leak seemed to have stopped and garage was closing for the day so I rode home.

On the ride home the engine continued to cut out when the throttle closed and I noticed the rev counter stopped working. When I got home found both carburetors now appear to be leaking a bit of fuel.

Any suggestions how to solve this? Is it a common problem that is easy to fix?

[Sid Squid]

When you were under the tank something electrical has been disturbed. This is evidenced by the tacho - driven by the ignition system - not working

Bike fixed, thanks to Yorkie_Chris phoning with advice. Thanks to Sid Squid for replying with advice above too.

Yellow and black wire had become disconnected when I put the air filter in, it's very easy to knock off when fitting the rubber hoses to the underneath as it is in the way. Bike now running fine with no petrol leaks so far.