I got an old 1970s Victa Mayfair low arch mower with 125cc that would only start for a second and then cut out. I swapped needles and it still hesitated to stay on but would at least do so after a second or third attempt, unlike before. I suspect there are other problems but it now cuts grass.

Ahh, if only victa had kept producing the thumblatch catcher series, they would be in better shape today!