If you had a good known engine, you could do a compression test and use that to establish a 'base line' as far as condition goes.
With a briggs, anything over 60psi and it will run. 80psi is better. But valve clearances can affect these outcomes.
Its not much harder to just pull the head off and look.
Sure you cant see worn rings, but for the 1 in 20 or so that smoke bad from worn rings you dont loose much on time.
Ive never tried on a Victa. But there are more variables than a 4 stroke.
With a Victa, its just easier to pull the muffler off and look at the piston/bore. If its not too good, check the inlet side (new o-rings here are a good idea anyway), if thats ok it will be fair, if its not its stuffed. Lift the starter off and check the bottom of the bore too, if it turns out ok, chances are it might have needed a starter o-ring anyway. Pull the head off if its not looking too good. Best idea is to remove or at least loosen the decomp and plug before you take the head off.
