Do you have spark? The connection between the cable and the cap is notorious for failing after you pull it from the plug. Reseat the cable in the cap.
The petcock operates by vacuum. If you reversed the two lines it certainly won't work. Try pulling off what you think is the fuel line from the petcock, then put a cup under the spout, then crank it over. Gas should flow. No flow, no go.
If there's no flow, then pull off the other end (near the carb) of the vacuum line, and smell it. If it smells like gas, you may have them reversed. If it does not smell, and you feel brave (or stupid), suck on it lightly and see if gas flows from the petcock. If there's still no flow, pull the line you thought was for vacuum off the petcock, push it on the other nipple, and try again.