2003 400ex shifting issues

So this past weekend I went riding at my buddy’s and it was running great, I stop for 2 minutes. Start it up and it starts making a clunking noice when I put it in gear, it wouldn’t shift into 2nd. So I brought it home and tried it again yesterday and I had too force it into 2nd and once I did that it ran great and went threw all the gears smooth. Today I hope back on it and it will not go into 2nd at all only goes to 1st and when I pull up straight to neutral