gotta make sure you really have spark. pull the plug wires while cranking and touch near an exposed bolt to see if you have spark in each cyliner. you'll be able to smell fuel so if you have both of those i would get the compression tester to see if you actually have compression.

even if it's a fresh motor, if the valves aren't adjusted after installing the cam you more than likely don't have compression. adjust valves, set the timing and try again.

seen it more than a few times.