Hi Grumpy, have worked out how to put circles and such onto photos. Sent the photo of gasket/insulator and put a circle around the flat part. This side sits against carby and unsure if it makes any difference.
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Have proceeded as you suggested and all holes between carby,gasket/insulator and flange on elbow do actually line up. Have found this though.
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Even with the gasket sitting against the elbow you are still able to see a tiny bit of sunlight through the two. I am thinking once attached to carby, because the bolt holes are on the edge, it may not be not sealing properly as all pressure is twisting elbow flange into a slight arc as to say. Hope i have explained this easy enough to read and understand.