If you have a good air supply,good fuel flow when you pull the fuel line from the carb and crank the engine over,good fat spark,and compression on the 500 should read between 50-90 psi(normally)because of the cam detent on the exhaust system,then sounds like you need to recheck this new carb. Air,fuel,compression,and ignition have to be right. Also the throttle slack must be no more than 1/8" at the thumb lever or the etc contacts will touch in the throttle housing retarding the spark. Plus here's something else another member found on his strarting problem.Look at his solution to his problem. http://forums.atvconnection.com/pola...ml#post3155476
May or may not have anything to do with your problem.

 

Already adjusted the throttle, that was my initial problem, when i had no spark. I have another carb, i put a another new one on it and see what happens.

 

Finally found a compression tester, only had 25 psi max

 

Hold the throttle wide open, crank over for several revolutions to get the maximum compression reading. If it's still less than 50 psi, either the valve adjustment is too tight,the cam detent lever may not be functioning properly,or you may have an internal engine problem.One other thing I can think of is to pull the recoil cover and flywheel nut and see if the flywheel woodruff key may have split,allowing the flywheel to move,throwing off timing. Have had that happen on the 500 engine several times. Clean the pickup coil and stator area while you're at it.Plus does it recoil start? Several posts on this when the pulse coil is dirty, out of alignment,or a weak battery and won't electric start but will with the recoil.

 

Going to be away for a few days, but, no, wont start by recoil, will check the cam detent lever and flywheel when i get back.