Clunky rear derailleur on lower gears

[Tin Pot]

To my eye, they look within tolerance but your rear view picture seems to be on the huh so it's hard to be sure. Align a steel rule across a larger cog and let's see.

Break the chain once and use a quick link to rejoin it. Makes threading it through the cogs and wheels so much easier, as long as you don't foul the jockey cage.

Something was clunking so I've taken off the wheel, derailleur, chain, front derailleur, band, rear brake cable, bottles, bottle cages, pedals, the handy bit for the derailleur.

Oh, and the pump holder, and black protection tape.

The chain has stretched, and the derailleur hanger was loose with one screw apparently threaded.

So I'm stripping the whole thing down! 'New' bike will appear in my other thread eventually.

 

[confusedcyclist]

I'm glad I stopped by, I'm having a similar issue on my new build, never bothered to look into what the B screw does!