Well you need three things for the motor to run
1) Fuel
2) Spark
3) Compression.
Not trying to be smart but those are the basics, any one of the three will keep it from starting.
If you have a compression tester check each cylinder to make sure it's got pressure. That way we'll know the valves are closing.
How long has the carb sat around ,did you clean it out, make sure the jets are clean. you can go here
www.sscycle.com and they will have a section on the carbs and you can download the full manual for a E G D etc. It will get you started on getting the carb setup right for starting.
Battery power, I would suggest you start with a load test on the battery to make sure its holding a full charge, even though a meter might say it has enough amps the load test will tell the truth.
Then go wire by wire check the ground, if you powder coated or painted the frame your star washer under the ground might not be digging through the paint and getting a good ground, so scrape a bit of paint away from the ground wire.
Check to make sure you're getting spark at each plug