G'day Virus66

Well you've come to the right place for help.
The 450407 is listed in the Model sheet for 1974-75.
Mod Bonnar Bloke will ask for some specific photos to ascertain
the transmission and frame condition.

The crank start is referred to as a trip-release wind up.
This one was used extensively on various engines in the 1960s.
It is novel that someone has put it on a horizontal Kirby!

Here is some stuff on the 45 (to read in the meantime)
https://www.outdoorking-forum.com.au/forum/ubbthreads.php?ubb=showflat&Number=64933

Hope this helps.
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Jack