[Dynamite]

Not to be smart here guys, but guessing at a problem only confuses things and makes it more difficult. As frustrating as trouble shooting charts are, they systematicly eliminate and narrow down possable causes.
My suggestions to narrow it down.
Heat the engine up to the conditions where you know it will not start.
Pull aone spark plug lead off and either use a tester, or a grounded good plug to see if you have spark. If there is no spark, the problem is ignition.
Dump a small amount of gas down the carb. If it starts, the problem is lack of fuel.
Let us know which way it turns out, so we can go from there.