I concur with midnight. A little O-ring grease helps keep things in place.
I later found my 73 850 did not have the O-rings and couldn't for the life of me locate this buzzing sound coming from the bike until one day I grabbed the headlamp while riding. Release then grab, release... I found the annoying problem. Like you say..."I'll try that next time." You can learn to live with it.
Cheers,
Tom
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