You certainly did good job cleaning out tank. Along with new petcock, we can assume petrol at least makes it to carbs. Let's re-arrange order for fastest results.
1. verify spark. Pull plug wire and insert spare plug. Ground case of plug to valve-cover and crank. Do you see spark? What colour is it?
2. test fuel. Use squirt bottle and spray 2-3cc petrol into airbox after air-filtre. Wait 30-sec, then crank engine. Does it run?
3. compression-test. with good numbers, you can skip next step
4. cam-timing and valve-clearances. Adjust to looser end of range, they tighten up with wear
