75 KZ400 valve adjustment nut problems

Okay, so i have been working on this 75 kz 400 for a while, i adjusted the valves on it and got it running sweet. However 2 days later i started hearing the rocker arms chattering a lot on the right side, so i pulled the inspection cover off above the spark plug, i found the nut that holds the adjustment screw for the exhaust valve backed all the way off. So i reset that valve and tightened the nut. At the same time i went over the other 3 with a wrench to make sure they were tight and they were. Fast forward to today, the rocker arm chatter was back, this time the nut for the adjustment of the intake valve was backed off. What gives? Why do these nuts keep backing off? Im out of ideas.

Old?
Try a hardend lock washer?

i was honestly wondering if there should be a lock washer behind there. It would make sense if there was one This bike has 4900 miles on it with no evidence of being tampered with.

No, no lock washer needed. Do you have a torque wrench for small work? I suspect you under-torque the lock nuts since they come adrift, but OTOH you do not want to overtighten them, either.

Nope, i have a torque wrench for small work, they were tightened to spec every time.

Sounds weird. I would try to raise your question here www.armbell.com/kz400/index.php?sid=de02...04a66fc&mforum=kz400