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Below is the actual sizes of Delorto 5mm jets, obtained by direct measurement. You can see the line has a different slope for the bigger sizes than for the smaller ones. You can also see what drill sizes correspond to what jet sizes.
Here is the engine side view of a Delorto SHA carburetor. At the base of the vertical brass “spray tube” with one or two holes in it, there is a tiny hole in the silver metal below the brass. It gets overlooked frequently. When it is blocked, the engine will not stay idling for more than a few seconds, but will otherwise run fine if the throttle is kept open.
