So there's only three things these engines need to run: fuel, air and spark. Here's my trouble shooting sequence (some of which I am sure you've already completed, but repeated here for completeness)
1. Fuel. Make sure you have clean fuel in tank. Pull hose off carb to be sure fuel is flowing that far.
2. loosen screw at bottom of fuel bowl to be sure fuel is making it into the carb bowl.
3. Crank engine (choked) and verify fuel in carb venturi
With these, you've mostly eliminated fuel issues.
4. Air. Do you have compression? is there resistance to turning the engine over? Do you feel the cylinder "sucking" air through the carb? Can you feel air being expelled through the exhaust? If so, you should be good.
5. Spark. This is where most problems occur. Is the engine timed properly? Does the spark occur at the right time in the combustion cycle? If not, it won't fire, even with a good spark. Follow the static timing procedures posted on this forum. Check the plug for good spark. Properly gapped plug, good plug wire, condenser, coil, points. That's it.
Good fuel, air, good spark (at the right time) and it'll run.
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