Sounds like throttle pump jet is too small , try the next size up and maybe adjust how much it pumps out

My 40mm solexs did this , and I adjusted the throttle pump rod to add more fuel , which worked cos I had the right size jet but wasnt pumping enough fuel through it

Good luck man they are a thing of art when tuned properly

Cheers boys and yeah they are brand new carbs ill try what you suggested and see how I go

An upgraded Fuel pump is not needed for a mildy worked A15. The stock Datsun mechanical fuel pump has adequate volume and perfect pressure for Webers.

I would try a larger accelerator pump jet if the carburetors "die" when the accelerator pedal is quickly opened. Also check the float level.

I use 32mm venturis on my A12 and get occasional popping (backfiring) on part-throttle, but the same thing occurred on the 1522 engine. I experience zero off-idle stumble.

The fronts are backfiring through carby from not enough idle mixture.
The off idle stumble is because of the big venturis. If this is an a-series.. 30 venturis and 40f9 should be better.
if the carbies are second hand they might need a new gasket kit applied.

Im assuming you know how to set float level and how to sychronise the carbies too?

From what my old man thinks it might be

34mm chokes
45 aux venturi
125 main jet
180 air correcter
F16 emulsion tube
45 f12 idle
50 pump jet

So if I go ahead and change the pump jet would it make a difference or make the chokes 32mm

Mhmm.. Well my A15 is mildly worked so I'm assuming "D" I will need a larger fuel pump.? Or what is the best way to solve this..

Will changing the jets make any difference

Sounds like it mainly needs more accelerator pump. This is common problem when using carbs too big for the engine.

Hey guys I really need a hand to tune my twin 45 webers..
The ute itself runs great on idle and when I push down the linkage slowly but if I am to push down the linkage quickly the webers them self die as though not enough fuel or air..
I have the first and second inlets backfiring and the exhaust make a poping backfire...
I am sure the timing right and the gap is correct I have tried advancing and decreasing the distributor and play around with the mixture screws but they are already screwed in all the way..

Any help would be greatly appreciated. . I really have no idea to get these synchronized correctly. .