Sounds a lot like a clogged emulsion tube (Main
jet holder) to me. It can pull fuel up with the holes clogged, but it does not aspirate correctly, so you get slobber down the intake instead of fog.
Just my $0.02. The ignition should already be advanced pretty far at that point, so I wouldn't think it would break down at a certain opening like that. Does it do it under load, and at a standstill with no load?