Honda-SOHC

I have got to the stage of trying to start my bike which came as a box of bits. IT won't start.
Carb jets were all very blocked.Slides seized.
I have cleaned the carbs and all jets are clear and slides and needles running free.
All four float bowls are filling with fuel but fuel does not appear to be passing through jets around the needles.
I have a good spark and good compression.
I have attached a picture of two tubes that i believe just vent atmosphere.
However when i apply compressed air to open tube end it will not pass through to inside of carb.
The tubes are new.
I have twice stripped the carbs and checked jets and floats.
Any ideas greatly appreciated,
Dave.

Can anybody help?
I am in the process off rewiring front end of 1975 CB750FO to existing wiring harness.
I have the wiring diagram for this bike.
I have fitted a new righthand switch (supplied by David Silver) but some of the colours on the new switch don't correspond
to the wiring diagram or colour match the existing harness.
The starter button works(black and yellow/red).
I have connected the Black and red to the matching black and red on the existing harness.
I am left with Black and blue wire?
And two black wires with white stripe.One has a male bullet connection and the other has a female bullet connection.
Be very grateful for any help.
cheers Dave.