If it has compression, carburetion and ignition it has
to run....So sayeth a wise old mechanic.
We will set compression check aside for now assuming you checked it before begining restoration.
Is fuel reaching cylinders...wet spark plugs?
if so proceed to check ignition
if not something is stopping fuel flow...check for everything from closed tank vent to clogged carburetor passages.
Ignition...just because you see spark jumping does not follow that spark is strong enough to jump gap
of spark plug when under compression.
Switch to a KNOWN GOOD spark plug...sometimes the
problem is a spark plug that looks good ,but, isn't
Even new from box spark plugs can be bad.
If the ignition is at fault it can be as simple
as a fouled spark plug or as expensive as a new
coil...inbetween are possible shorted wires, dirt
oil, glazed points,loose or corroded connections
and the always possible..."I don't know what I did
but I fixed it" after taking system apart and putting it back together a few times.
Good Luck
Louis

thank you very much for you time

What brand of magneto Eisemann or Wico? Also which
model...usually on magneto plate. It appears from
this end of internet that problem is magneto related.
It is not enough to have a spark...it has to be a
strong spark, 70 year old motor likely has original
coil,condensor and wiring.
Louis