Greetings Tiztom, and don't worry about the 'life story'! TMI [too much info] is always better than not enough, in this game. grin

It's certain that you actually have an LM carby, as the G4 was only made for a year or so [Correction; three years - mid 1975 to late 1978] - and that was long before Victa brought out the first Tilt-a-Cut edger.

As far as resizing the jet goes, I'm afraid your 'guy' is full of it. Totally unnecessary - after all, we sure ain't talking about a high specific power output racebike engine here.
Like the Yam TZ350 donks my bike mech has built - 100hp @ the rear wheel!

You can download a workshop manual excerpt on the carby from this page - Section 4; https://www.outdoorking-forum.com.au/forum/ubbthreads.php/topics/54967

I don't recognise the 'small helical part' you describe - it may be a 'stripped thread artifact', caused by the self-tapper, though.

Last edited by Gadge; 18/03/17 10:36 PM. Reason: correction as noted
Cheers,
Gadge

"ODK Mods can explain it to you, but they can't understand it for you..."

"Crazy can be medicated, ignorance can be educated - but there is no cure for stupid..."