Isn't this covered in the FAQ somewhere?
Until 1977, the carbs didn't have accelerator pumps. Without these, you can't snap full open the throttle from idle, or the engine will just wheeze and die. It should, however respond nicely with 1/2 throttle rotation with very good response.
Also important for this question is whether you have the stock air filter and to a lesser extent stock exhaust, which you neglected to mention.
The throttle response on the stock bike relies in part on rich mixtures during low rpms such as idle. The idle jets and air bleed screws determine this, but are affected by air filtration changes. Stock air bleed scew setting may not be appropraite for bike with air filter changes. And, turning them in may help the throttle response, to a point. The adjust screws have a limited range. Larger, or perhaps cleaner, slow jets may also help throttle response.
It is also possible that the cross drilled holes in the emulsion tubes behind the main jets could be clogged. This could diminish the extra charge of fuel from the needle as the throttle is opened.
Finally low fuel levels in the float bowl can also make the engine run on the lean side. What are your float heights set to?
Or, it could be none of the above...
Cheers,
