STOP!
based on the description of the problem it appears that fuel is leaking past the o ring on the needle/seat on one or more carbs.
You will probably see fuel coming out of the vent on the offending carb. Don't make this harder than it is
What needs to be done to fix? Only thing that's changed is the fuel filter.
As mentioned by others, you probably have some debris that you dislodged, could be small chunks of rubber, rust, crap, etc, etc,...you need to remove the needle seats from each carb and clean them, they are very delicate, they can be removed by removing the locking screw, then unscrewing them up and out of the bowl top, no need to remove the bowls, you'll need to reset your fuel levels after re-installing them, remove them, look for debris, some compressed air, and cleaner, make sure the needle seats actually move and seat in the assy
Mike
