ok, first thing is float level,,, you`ll find a number on the top of the weber to see exactly (hopefully) the "type" of weber it is so enables you to determine exactly what float level you should be running,,, set that up first
then move onto things like the pump by-pass jet (in the bottom of the float bowl),,, sort that (by simply blocking it off (solder it up- whatever)
then we can look at things like making sure you havn`t for the vent at the rear (air-filter base plate) hole blocked off by the filter base plate being fitted up-side-down or something stupid like that
then we can work on the "Making sure" all the jets & passages inside the carb are actually clean (typically not)
we can also look at making sure that the venturys are not fitted incorrectly (blocking of the mains supply) etc
ther,,,, see-ing as the jets are pretty damn right (for staters) & that with those jets it should run sweet as a nut (basically by rights)
then obviously if youy`ve done all that right then you should have a decent power curve without any hesitations
Providing your cam isn`t a monster full race dog of a thing cause-ing all sorts of "Low-air-speed-reversion issues or similar effects from many "Other" different variables
but still,,, .... ,,,, do all that & get back to us
OH!!! make sure you have a least "One litre of fuel per minute" fuel supply before you do much else from the above list
then when you`re sure & double checked all that,,, well """THEN""" we can start to """TUNE""" it with you yeah???
now get to it,,, report back when it`s all done ok???