While doing some research on Google on carburettors I came across this note about the maximum downdraft angle for Amal MKII Concentrics:
https://vintagebikemagazine.com/technical-articles/amal/Triumph 1979 T140 with MKII Carburetors update:
When using a MKII carburetors on a Triumph for off-road, or racing, it is possible to use European jetting. This jetting is for stock pistons and mufflers. Any modifications to compression or exhaust will require different jetting.
The Amal MKII is limited to 15° downdraft with the pilot jet in the bowl. If the downdraft is more than 15° you must move the pilot jet and blank jet. Put the blanking jet in the bowl and the drilled jet in the body.
This subject also came up on the Vincent Owners Club website with same answer to prevent engine flooding.
Measuring the downdraft angle using a combination square and Mark I eyeball I got 22 degrees. I will have to check where my pilot jet is. I have not come across this before. If it is in the wrong place that may be the cause of my engine flooding problem when the petrol tap is left on.
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