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Barend shifter problems
I am in the process of changing aerobars on one of my bikes and changed my 8spd barend shifters to the new bars. However the rear shifter has now lost some of it's range for some reason. It will not index 8 cogs, but only 4. I cannot see that I have done anything wrong on the install and have installed them on several of our other bikes with no problems and they were working fine on the old bars.
I've seen this issue pop up occasionally here, including a somewhat recent thread late last year. On that thread, a member clearly described the steps to resolve the issue. Unfortunately, I'm not having much luck locating that particular thread now. Perhaps you might find it.
In any case, I have experienced the same (or similar) issue. Apparently I fiddled with the lever a bit prior to installation, thereby losing my full range of indexing. The "fix" was simple; I needed to get the lever back to the first detent. To do this, I moved the lever to its lowest position, then removed the lever fixing bolt. I then removed the lever from the lever boss cover and repositioned it at the top position. Again, I rotated the lever down until I reached the first detent. Finally, I repositioned the lever to its correct position on the lever boss cover, secured the lever fixing bolt, and completed the install.
Note that this is how I recall resolving the problem, but I certainly didn't word this as well as others have. Also, there was no cable in the shifter at the time. The key seemed to be using the lever boss cover to reposition the lever...almost like "winding" or "unwinding" it.
You probably need to take the lever back off the body and rotate by 90-degrees (disconnect the cable from the rear derailer first).
Yep ... been there, done that.
What usually happens is they are installed straight out of the box so the relationship between the shifter "inards" and lever range of motion is in sync.
Then you decide to change things and you take the lever off while the shifter "inards" are in mid gear position.
Since the "keying" of the shifter can be on any side of the square anchor point and the "inards" are shifted by about 90°, it is very common to be able to reinstall the shifter lever in the low (cable slack) position while the "inards" are still in the mid gear position.
Then you set/adjust your der up only to find the lever stops after shifting only four gears.
Like Gonzo Bob said, you will have to disassemble the lever off the square anchor and remount the lever on the square 90° away from the low position.
Before doing this make sure you shift the "inards" as low as they will go. Then dismount the lever from the square and remount the lever/"inards" 90° from the low position.
Once the lever is at least engaged with the square, you should be able to down shift the "inards" to their low position. The "inards" low position and the lever low position on the shifter mount are now in sync again.