I do not file the half moon cut straight down the carb as in the photo above.

Rather I angled it slightly so that it forms an angled lip instead.

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Also it is - NOT - a good idea to replace the SuperTigre provided plug with an O.S. A3 as suggested.

The A3 has a short profile, while the ST Plugs use the longer "nose" to prevent the element from getting fuel soaked.

In the following picture you can see the ST plug as the second to the right. Notice that it is just as long as an O.S. "F" plug, while the O.S. A3 plug on the right is considerably shorter.



This is a mistake I've seen many people make.