Dunno! If it's CyberJack's changing sig line, it wouldn't be intended personally...
To get back to our muttons, see if
THIS PDF doco from the ODK Victa Manuals & Parts Lists section will download OK for you.
This covers both the early 'Sure Start' and later 'Trip Release' [TR] types of impulse starters.
If you have the TR type, there are two common faults that cause the 'freewheeling' you describe.
One is the main spring is broken; the other is that the 'release dog' is not engaging the teeth on the main spring drum. The latter is usually due to the dog return spring having broken.
Easy to check which it is; take the starter off, push the trip lever in, and spin the winding handle [clockwise] while you watch if the spring drum spins. It shouldn't. If it does, new dog assembly time. If it doesn't, and the handle still spins freely, it's a busted main spring.
In the later TR units, the release dog is a non-serviceable Zinc alloy cased assembly, not the discrete parts shown in that 'Old Starters' doco.
If your unit is cactus, I would be taking advantage of IHWS' very generous offer, if I were you.

There are still a few NOS dog assemblies about. Part Numbers to look for are: Victa ST12213; Kirby GED253; and in the US, Tecumseh 31419.
Main springs are another matter; they do come up on FleaBay but are getting exy.
The TR starter uses the double wound spring, which looks like this.
Edit: These springs are NLA as a new part [Victa discontinued them around 1990], but NOS ones occasionally pop up on EBay.
Part numbers, for reference [sellers often don't quote these], are Kirby GED270; Victa ST12233; Tecumseh 31413.