I don't know if this ever happened to you guys. I installed some new ngk spark plugs on my cb350, installed it as the instruction says (hand tight and 1/2 turn with wrench) no problem there. I went for a ride for a couple of miles, let it cool down to check the plugs. Here comes the problem, I tried installing the spark plugs again, this time I can hand tight it in, but trying to torque it not even 1/4 turn feels like im gonna strip the threads, there is no way I can go 1/2 or even 1/4 a turn. The thread looks fine for both the plugs and the head. help?