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I have no experience of the Binks but it bares so much likeness to the Amal that I’d bet that the working principle is pretty much the same.

Even if examining the needle with an eye loupe identifies the groove used you still cannot guarantee that it is the correct one!

Your mantra should be: Assume everything is wrong, believe no one (Including me!) and take nuffink on trust until you have proved it!

Look at it from the designer’s point of view; I’d give you really good odds that the float was designed to sit half-and-half in the float chamber when the fuel is at the correct level. If this results in a fuel level that also happens to come half way between the main jet and the bottom of the carburettor’s choke then you ‘aint going to be far out. In truth as long as the main jet remains submerged under full load the fuel level will never be too low.

Unless and until you can obtain or make a new needle the old one is best straightened by laying it on something flat, a piece of modern glass will be just fine and roll it to find the high spot. Once located put piece of card under each end and press down, you may or may not see an improvement when you again roll the needle depending on the springiness of the material. Increase the thickness of the card little by little until you are satisfied.
A much better way is to use a lathe, preferably with a collet chuck. With the needle exposed to the first groove check for run-out and correct by a judicious use of a piece of brass with a horizontal groove in the end held in the tool holder, advance the cross slide by degrees noting the position of the feed dial each time, progress down the needle groove by groove correcting as you go. By this method you should be able to return the needle to near perfect straightness with little risk of overdoing the bending and remember that to bend the material you are taking it beyond its elastic limit so care is needed.