Would anyone have one of these pawl nuts by any chance. Fits 60s, early 70s Victa 2 stroke with the G3 carby and wind up starter. It threads on to the top of the engine shaft above the flywheel and fastens down both the pawl (starter cup) and flywheel. It is a special fit nut, being 1/2" internal BSF thread. I know it must be this size because I recently purchased some BSF 1/2" locknuts for another project and they fit perfectly. UNF lock up after just a few turns of the thread.
I took one off another Victa mower to show what they look like. I have a few of the old Kirby Lausen type, but they are an even smaller thread diameter and probably UNF in any case.
