^I think the fuel tap is the first port of call before the needle. If possible he should test with a tap he knows that flows well.
I do a visual check by seeing how fast it pours out of the fuel line. There generally should be a steady stream off fuel rather than dripping of any sort.
An ultrasonic cleaner on the tap filter stick would be worth a go as well. I immersed mine in acetone in a small jar before putting that in the ultrasonic cleaner water. After about ten minutes I noticed the stubborn varnish start to come out of the filter.
Ahh, if only victa had kept producing the thumblatch catcher series, they would be in better shape today!
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