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EFR215’s comments about measuring petrol level seem to have ignored the significance of the position of the float chamber relative to the carburettor body….Swing the float chamber rearwards and the petrol level relative to the carb body is increased, and vice-versa. The correct position of the float chamber is central to the curved cutaway shape in the top edge of the crankcase, provided that it hasn’t been modified. It follows from this that there is no need to start cutting new grooves in float needles….Just swing the float chamber backwards or forwards as necessary.
Please also bear in mind that when starting from cold the float chamber will have been flooded by the use of the tickler button, and this temporarily puts the petrol level well above the pilot airway level.
Amal 206/151 carbs on earlier Flyers are different to the later 206/151R carb as the earlier ones have a totally different primary air system with 4 external holes around the lower part of the mixing chamber. The later carbs have the primary air inlet just inside the bellmouth. The change happened in 1939, when Government buyers of BSA’s, Nortons, etc., quite sensibly insisted that ALL air entering the carb had to be filtered, and of course that wasn’t possible with 4 external holes to be included. Quite when this change filtered down to carbs being made for Scotts, and how long it took for old stock to be used up first, is anybody’s guess.