NEED HELP with engine issues 1974 GT550

[BDcycles]

I am certain the pilot jet is clear. Although I have blasted and blasted the slow circuit passage with carb cleaner and compressed air I question whether the passage thru the carb body is still partially obstructed. It does pass a decent amount of cleaner when spraying it. I don't know what to do to be certain the passage is clear.

[GTandcbr]

Just a thought. Have a look at the centre carb throttle valve. It should have a number stamped on it indicating the cutaway size. This cutaway effects how much air enters the mixture between 1\8 th to 1\4 throttle. The lower the number the richer the mixture is. Too rich will foul the plug at idle