Thank you for your responses!

So the jet sits inside the mesh filter? With the narrower end pointing down?

I had another thought: does the position of the 'hinge' that connects to the engine block from this linkage (circled in yellow below) matter, or is this just where it is? (sorry bit hard for me to picture this with the cowl on)

[Linked Image]

Here are the engine details. I will try to have another crack at the mower today and will report back.

[Linked Image]