what fuel should I use?

This may seem a stupid question but please bear with me as I am a total beginner about to take delivery of my first engine. All I know about it so far is it is a JAP 4 stroke from the 1940s or 50s. I will be coming back to the forum for some identification help when I can get more details.
What I want to know is will it run on unleaded petrol or do I need to mix with some form of additive. If so what? I would hate to spend time and money on it then ruin it by putting in the wrong fuel. This is my winter retirement project and the first time since I was a teenager that I have tinkered with engines so it is highly likely I will be coming back to the forum for help.Any help would be appreciated.

Unleaded fuel will be fine, leaded fuel didn't exist when most of our toys were designed.

Pete.

it is a common question to be asked mate
and yes a pete foden says streight from the pump is fine
when i first started i bought a cartridge you dropped in you fuel can
results were running very hot and popping and banging   
so that was removed and never looked back since with any of my engines from amanco bsa jap jlo lister petter wolseley villiers even a worthington i borrowed for a while
kev