Crazy 2012 kx450 issue...

I’m having the same problem 2012 KX 450F just started Learning how to wheelie yesterday I finally 12 o’clock, then scrape my fender I was so happy I parked the bike and got off and put it up for the night I wake up today bike start up fine wheelie down the street bike was running for like five minutes. I was cruising going slow in first gear and the bike randomly shut off bringing me to a stop then put the bike in neutral kick it over. It starts right up. I’ll drop it in first gear. Try to takeoff 3 feet and randomly shut off again then the kickstart felt like the motor was locked up, so I pushed the bike around the corner home and tore the top and apart the spring is on the exhaust cam and the clutch side and stater side is good no physical damage piston good valves good put everything back together and try to kick it over. It’s easy then it gets hard then I got it started roll the bike around the corner one time then it did the same thing again easy to kick, then get hard then the kick start acts like it’s lock up again I wish I would’ve thought about this the first time but I put it in gear roll it backwards and everything‘s fine then its easy to kick then it gets hard to kick.