What shifter are you using?

Sram S900 tt shifter

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Oui, mais pas de femme toute de suite (yes, but I am not ready for a woman straight away) -Stephen Roche's reply when asked whether he was okay after collapsing at the finish in the La Plagne stage of the 1987 Tour

Is the cable around rear mech in groove running to the pinch bolt? Can you post a picture. Have you set limit screws? I do the limits before connecting cable by just pushing mech by hand

You need to be pretty specific with the B-Gap adjustment screw as well. There's a couple good videos on YouTube showing how to set up the derailleur.

https://www.youtube.com/...gBY9LLI7c&t=254s

Explain your setup process.

I set it up per Sram's oh so helpful instructions and as outlined in the video link above. They were slightly different, so I tried both ways to no success. On a whim, I added a few links to the chain and tried the setup process again with success. I had the process correct, but just needed a longer chain. Not sure why that would be but it worked.

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Oui, mais pas de femme toute de suite (yes, but I am not ready for a woman straight away) -Stephen Roche's reply when asked whether he was okay after collapsing at the finish in the La Plagne stage of the 1987 Tour

Thanks for all of the ideas and helpful suggestions. As a burgeoning diy bike mechanic, it was reassuring to know that I had tried most of the suggestions given by the posters, but frustrated because that should have been enough to work.

What ended up working in my case was adding 3 links to the chain from the recommended length by Sram. This allowed the b-screw to be adjusted properly. With the b-screw adjusted, it works like a dream. So glad I went to a 1x setup.

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Oui, mais pas de femme toute de suite (yes, but I am not ready for a woman straight away) -Stephen Roche's reply when asked whether he was okay after collapsing at the finish in the La Plagne stage of the 1987 Tour

1X is extremely sensitive to two things:
- B-limit screw spacing
- chain length

One key thing to remember is that the jockeys on 1X are 12T instead of 11T. What this means is that, if you use the standard sizing for a chain (wrap around the chainring and the largest cog and add two links), you need to add TWO MORE links.

SRAM 1X derailleurs are STRAIGHT parallelograms, not SLANT parallelograms. This means they move strictly in the horizontal (in/out) axis. The B-limit adjustment is entirely responsible for up-down movement of the pulley cage. On a slant RD, the RD moves down as it moves in, but this can cause ghost shifts (not likely on the road, but still a potential issue). So that means that you need to have the B-limit set precisely.

But B-limit spacing is ALSO influenced by chain tension, which is of course influenced by chain length. A chain that is too short will result in too much tension in the lowest gears (largest cogs).

If you find that you can get it to shift in EITHER the lowest gears OR the highest gears, your chain is probably too short. If you are having more general trouble shifting, it's probably the B-limit.

VERY ROUGH rule-of-thumb: for SRAM chains, which are 114 links, 86-Chainring-Largest_Cog = # of links to remove. I.e., 50-11/32 --> 86-50-32 = 4.

But that's definitely not hard-and-fast. But on all of my bikes, that rule holds true.

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"Non est ad astra mollis e terris via." - Seneca | rappstar.com | FB - Rappstar Racing | IG - @jordanrapp

What confused you was that you set up chain length for a too small biggest cog.
The geometry of that derailleur is setup for a much bigger 1st gear and 11 speeds.
So when you set your chain length you needed to add in the amount of links required to fit around an imaginary 11 cog of the bigger tooth count that the derailleur was optimised for.
This then puts the top pulley within the require range to be fine tuned by the B screw.

This is because of the offset of the top pulley to the pulley cage pivot point does the control of the slant movement and you effectively set the chain length up in second gear, so the effective slant angle was wrong.

This is a really good post in regards to layman's knowledge. When you are done your pro triathlon career you should become an engineer or something.