Sorry, I missread your post first time around. You need to determine if it's a spark or fuel problem. If the engine will run even for a few seconds by pouring gas in the carb, then you need to check out the entire fuel system, tank, lines, fuel pump etc, all may need attention. Next while cranking you need to find out if the plugs are getting spark, you can use a clamp on timing light, if the light flashes you should have some zap. Also you can put a probe type voltage tester between the end of the plug wire and ground, will flash.
And as mentioned timing could be off a bit. If all this fails you need to begin a complete tune up starting with a compression test etc etc. Best of luck.
