I am in the process of finishing a build, DB Ridge Runner frame, Shimano 7sp HG 13-30 casette, Deore II RD, Shimano 7 sp bar con shifters.

I slapped it together intially to test it and see how much I liked it, and ended up loving it, so I tore it down, PC'd it and am now finishing the build.

The challenge I am facing is I cannot get it to shift correctly now. On the initial build, I used a used HG chain and it shifted beautifully. On the build I bought a new SRAM 870 and I cannot get it to shift right. I keep playing with tension, but I cannot get it to shift up or down consistently. I am debating going back to the HG, but I have to go find a pin and I just can't figure out why the 870 is balky.

Suggestions?

The problem cannot be with the chain itself; I have used that chain with 7sp HG friction and indexing setups many times. Have you checked to see if you have a binding link? What is the exact model of the bar end shifters you have?

Links are all good, nothing binding.

Where do I find a model # on these dumb shifters, usually Shimano makes it pretty obvious.

I believe they are the SL-BS50 7 speed.

I am just confused why it worked perfectly with the old chain. The only change from the previous build is a narrower BB spindle and the chain.

The shifter has only 6 clicks, correct?

I'm not sure where the model # is found.

Yep, 6 clicks

So, using calipers, the SRAM measures .275 and the Shimano HG measures .279.

Enough to make a difference? I am leaning towards yes, at least on this build.

I have to go buy a pin to test my theory.

Perhaps it's a one-way chain.

Is the RD moving when you shift?
Try running through the gears without the chain, see how that setup is going.
The SRAM comes with a master link, so it's not the normal Shimano pin failure.

I'm not confident that the chain size difference of .004 makes a whit.....

Replacing the chain is primitive and simple. Re-running cables/housing after a repaint, now that's a more likely scenario for an issue.

Are you going OK then "losing" a shift? Almost sounds like a housing caught on a ferrule, a cable guide snafu, or a cable not sliding well. I'd double-check the entire cable route, each connection and ferrule, make sure all is OK in that regard. I'd also make sure the shifter was "zero'd down" when the cable was inserted (a common error on STI's, not sure about MTB's...).

If you can't fix it, I'll pay shipping, and you won't have to worry about it.

You, sir, are a prince.

You are correct that the chain width did not help.

I am about to try my old cable and housing

Are you being completely forthcoming with us, Preynmantis? Hmm?

Is the cassette new or used?

It would appear that the Prey'n Mantis is also less than forthcoming.... Yes, I had used new housing.

So, the moral of the story is "Pay attention to your housing"

Looking closer at the shifter housing, it was built like brake housing, despite the fact it was narrower. Used the old housing and it is working like a champ again. <dumb me>

Thanks everyone for the help.

I have some new housing (correct housing) on the way.