This item is an amended (lipped) type of bottom main jet holder, to fit early Amac carburettors - i.e. the HYK type, as fitted to Douglas 2 3/4hp Models (as listed 1919-21 as part number 1644D). The same jet holder may have also been used in other similar Amac carbs of the period 1912-25.
The original Amac type main jet nut design relied on a very narrow chamfer to create its seal, when screwing it in to secure the float chamber, which does not seem a particularly good design - especially when you consider that the original Amac float chambers (as shown in the photos) that were sold with these carbs had a nicely machined flat bottom face - just crying out for a seal with a red fibre washer, which of course, was what many other later Amal designs employed to secure floatchambers.
Certainly - when restoring my own 1919/20 Douglas 2 3//4hp model, I found that the original (and mostly unmolested) Amac HYK carb that came with it, had a particularly graunched main jet, and although I did initially try to reclaim it - it continued to leak heavily. I also have a second similar original carburettor - where the original plated main jet nut is shown in the photos. This is still in good condition - but when I examined it closely, I could see how narrow the sealing chamfer looked - so decided to make a small batch of nuts, as shown here - which are instead CNC machined from 0.875" brass bar, so that although identical in most other respects - they now offer a large 0.875" wide lip, that allows for a wide red fibre washer between nut and float chamber, to prevent leaking.
It should be noted that special attention was paid to ensuring that when using the red fibre washer (supplied), the final position of the main jet, in relation to the main Amac carb body should be the same as the original Amac main jet nut.
We use high quality red fibre washers from one of the top manufacturers, and two will be supplied with each nut - although only one washer should be fitted - the other being a spare (the top face of Amac floatchambers do not need a washer - they rely on a taper, which mates with a similar taper on the main carb body).
Price is for (satin nickel plated) brass jet nut and 2 red fibre washers (the original Amac main jet shown in some of the photos are not included in the sale)
Update October 2022: These items have now been Satin Nickel Plated - as would have been the original finish. Some of the photographs for this item were taken before plating (i.e. bare brass - but the item you are ordering will come Satin Nickel Plated
Price reflects complexity of CNC setup for this item (approx 12 different tooltype/multiple ops required!) and small batch number produced.
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