Did you put your petcock back together right? Disconnect the hose and see if you're getting gas when you turn your petcock on(or if you're not sure how much gas is in it, to "reserve").
Did you adjust your floats at all? If you made a big adjustment, double check that you measured from the right spot. Also make sure they're in there the right way -they can be put in upside down.
If you're working in a pan or don't mind getting some gas around, you can connect up a gas supply without the bowls and check if fuel flows through the bowl inlets.
When you run into problems, you have to logically go from one thing to the next and determine where the problem is. In this case, you have to start at the tank and figure out where gas isn't flowing. Ruling out the tank, petcock, fuel line, carb in, carb passages, bowl in. Once you have gas in all those spots, if you have compression and spark at close to the right time, you should be able to run. If not, I'd check to see if you have spark by pulling a plug and grounding it against the engine and turning it over with the ignition on. And check to see if gas is in the cylinder(on the plug when you pull them after trying to crank).
Since it's a new to you bike, I'd do the whole tuneup routine -make sure the valves, points and timing are set, that the right plugs are in it their condition and gap, check the quality of the spark and the resistance of the plug boots, check the resistance of the coils, new oil and filter, check the air filter, carb sync, etc.
It's not as overwhelming as it sounds once you've done it a few times.
