Hello,
Be methodical and start with the basics
Dissconnect fuel line before pump and check for fuel
reconnect and dissconnect pipe after pump.get friend to turn over and see if fuel pumps out .reconnect pipe.
check that fuel is spraying in the carb when you press throttle.manual choke ? check its working.
Check ignition. quick check is take no 1 lead off hold with a spare plug in against case and turn engine with ignition on by hand.You should get a decent spark.Dont hold the plug though! ,just the lead.Check it sparks with the pulley notch at the crankcase join or thereabouts .
Also check your points gap is around 0.4mm.
While its at no1 firing position check your valve clearance for that cylinder and then do the 2,3,and 4.
After that do a compression test with all plugs removed first.
if that doesnt work .Sart again but keep it methodical.
if your engine fires when cranking and stops when you release the key,Check the ignition switch.or try a permenant live to coil just to eliminate it.
Good luck