Kx250f not starting and don’t know why

I have a 2004 kx250f which refuses to start, new piston, cylinder is perfect, ring gap is fine, timing is right, and sparks good, shimmed the valves, and It still refuses to start with fluid. I know for sure the spark is good because I messed up the timing the first go and it would shoot flames out of the carb. The bottom end is also rebuilt too professionally! The valves also don’t appear to be leaking. When I got the bike you could only bumpstart it but it was running incredibly lean and wouldn’t idle. The second it was in my garage I tore it down and haven’t seen it run since. Does anyone have any idea why? Spark is good, compression is good, timings good, I’m so lost