I never bored my MC21 F3 carbs and it went very well.

You try changing the needle position on a set of '28 carbs compared to a '21. You'll soon decide to run '21 crabs. They are much nicer to work with.

As with most things on a '28 they seem to be a step backwards. They do look like nice little carb though.
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If I have to take the carbs off once more...