I went to put my valve cover back on my 400ex after a little servicing and found the threads in the motor were basically gone. The bolt would slightly tighten but not enought to probably hold the bolt in. Its only one cover bolt. Should I worry about it or would it be alright to just leave it off? It seems it would be quite a big deal to put new threads in it. Would it hurt leaving it off?

 

Most likely won't hurt anything,but you could always helicoil it.Good luck