I don't know those shifters so excuse my ignorance if there is a complicating factor. But it's most common just to have a shifter pull/release a set amount of cable. So you normally do all the adjustment at the derailleur.

When you say you can't get it right is that something like working for the first few gears and then not shifting immediately in later gears?

Have you changed anything with the cassette or rear derailleur?

I’ve got that bike and still ride it, but have changed it all over to 11 speed. I did recable it in the past with those shifters and didn’t really have any issues to get it dialed in. The thing that I do remember is that I would make sure that the “index” of the shifter was set all the way back to allow all the cable out. I would pull on the loose end of the cable and keep pushing the end of the shifter to shift, I want to say shift down but don’t really remember.

But then again I’m only the guy who wrenches on his own bike for fun, no real training.

Basically they don’t click at all— that’s what’s weird. I’ve done it with road bike STI levers and with downtube shifters before, but those never had this happen Best guess is screwed or unscrewed something I shouldn’t have when trying to figure out how to get them out of the bar— there are a few different tiny hex wrench screws in there and I’m not sure what some of them are for.

My guess is it's something to do with the tension in the cable. I'd do what's mentioned above and have the cable in one hand, removed from the frame cabling, so you can test the tension manually while trying the shifter with the other hand. If you get a feel for the tension needed and satisfy yourself that's part of the equation then you can move to setting it up connected to the derailleur with more confidence.

Assuming that works I'd also make sure when you put it back together the cable isn't routed oddly, like tight corners it can snag on.

A good suggestion, and that’s what I did— couldn’t get the rear shifter to “click” in either direction. It’s not fully seized up; the lever moves and the button moves slightly, but they don’t click into the different index positions. Really I think the only thing that will help me (though more advice is welcome) is seeing a schematic of the shifter so I can try to understand what I’ve done to it.

I scanned the usual sources and it would appear the most likely culprit is the shifter not being in the correct position. From what I have read to work properly these shifters are very sensitive to cable tension and they have a non-intuitive ratchet mechanism which means it isn't obvious what gear the shifter thinks its in. One solution appears to be to absolutely max out the tension and hammer the gears until it starts to sync but I would guess this correlates to the high number of people who complain about snapping cables with these shifters. The last post on thread provides a list that seems to take a logical approach to setting this up:

https://forum.slowtwitch.com/...ifter_Woes_P4301445/

I have not found any internals from the shifter but from what I gather they are a bit like indexed normal shifters. The rub seems to be that you can install a cable with the shifter being in any number of internally indexed position. Have no idea how this is possible but it means you can end up with a lot of issues if you don't take time to align things during the install. Having the cables 'settle' after install also seems to be a common complaint which again would occur if the alignment wasn't spot on during install but later shifted into place during use. If anything put a lot the system under a lot of tension to get it running and then back off the tension a bit after its all set up.

If you decide to replace the shifters I have a brand new set of 10 speed dura ace shifters in the box looking for a home.

That’s a tempting offer, as I can’t think of anything else to try with these. How much are you asking?

Looks like they're going for ~$100 on ebay, so how about $50 plus shipping?

I can't argue with that! Sent a PM

A B12 is a fast bike. You are not giving much against the fastest bikes per the age of peak aero paper. You can search for it in this forum. Secondly, you can change your shifter for Shimano or SRAM depending on what your derailleur is. You can probably upgrade to 11 speed just by changing them and the cassette. At least I did with sram red 10 speed.

You’re not wrong! No complaints about the bike except that the engine is currently a bit heavy and inefficient :). The only reason I’d like to get a new one is to have one with well integrated electronic shifting. Shifting from both the base bar and the extensions would be a game changer for me. I don’t want to dump out $1-2k though into a bike that I’m sure is worth less than $1k, so that’s a long term pipe dream for when I strike it rich on GameStop or something :).

Absent that I don’t really see a need to change to 11 speed— my road bike is all (gasp) 9 speed Sora and I’ve never had any complaints there. I just need working shifters now that I’ve destroyed mine. I heard back from Vision/FSA/ whoever they are today and they confirmed that they don’t know how to fix them either.