Keihin PWK, PE, FCR and Mikuni carburettor needles

The needle hangs from the slide and meters fuel between a quarter and three-quarter throttle. When worn, it richens the mixture and makes the engine hesitate in the mid-range.

The type (three letters on Keihin needles) is stamped on the original needle and given in the bike’s manual. The clip position then lets you fine-tune.