Whats wrong with my bike?

So here is the deal. I have a 2005 RM-Z250F that has been sitting in my garage for two years without being touched. The bike worked fine before I stopped riding it.

So i started by kicking it a million times, then tried to push start and nothing happend

So I took the carberator off and cleaned it out real good, also drained out all old gas and put in new.

Then bike still would not kick so I pushed it off and it started and road around for about 30 min.

Then later that day I tried to kick it and it started.... but

The next day I went to see If i could start it by kicking and nothing happend, so I tried to roll it off and that would not work either.

So next I put a new spark plug in it today, tried to kick and nothing would happen... but when I tried to roll it down the hill it started right up and road around fine.


My main question is what could be wrong so that it would start by pushing it off but not by kicking? There seems to be a decient amount of pressure when kicking.

Could It need new valves? I raced the bike for two years and only had the valves shimmed twice, but never replaced...

Thanks for any input!