bike dies when you shift

I was riding my 83 DT80 today.
I was going down a hill in 4th when I hit a bump, the bike started to die, I downshifted into neutral and it acts normal until you try to put it into gear, then it just dies.
I drained the oil and there were no metal shavings in it.
please help! also is it worth it to fix the bike? or should I just part it out?
thanks.

never mind, got it fixed, the neutral switch came unplugged.