Re: Finished build, won't turn over. :(
Did you clean out the gas tank before you mounted it? There is usually lots of crap in there, it might have clogged the filter right away (in the top of the fuel valve).
Pull the plug and take a look at it, do you see or smell gas? Is the plug soaking wet or dry? You need to find out if fuel is getting there... If your plug is soaking wet, dry it out, then let the clutch out and roll the bike around a bit so the motor turns over and pushes out any built up gas from the cylinder (make sure the plug wire and any other spark/flame is not in position to ignite fuel that may be ejected from the spark plug hole). This will clear a flooded condition. Now put the plug back in and give her another try.
Post back more details if this doesn't help and we will try to get her running....