Chain Stretch.
I was riding this am and noticed even in a midrange gear my chain was making noise against the guard on a bumpy trail.
When I got home I checked and noticed that it the highest gear the chain is just really sloppy and I ordered a new freewheel with an 11 tooth 7th vs 14 so it would really get loose. Even in first it’s either a little long or just a really weak tensioner spring on the rear derailleur.
Have to admit I’m a little surprised by this as the bike doesn’t have that many miles.
Im going to dig up my chain breaker and take a link or two out. Any one else see this is a newish bike?