Arrrgh....

Randomly throwing parts at it hoping you'll replace whatever's wrong along the way is NOT the way to go about this, all you're doing at this point is increasing variables, when you need to be eliminating them.

Like was stated above, you need three things for boom. Spark, Fuel, Compression. Check to make sure that you've got spark at all the plugs, check to make sure you've got good compression on all cylinders (that could point out a cam timing issue) and make sure the carb actually has gas.

99% of the time, it's something simple that's overlooked. Good luck out there!