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I have a 7-speed indexed twist-grip gear-shifter, but it was set up incorrectly: it has eight positions, the fourth is where the numbers start showing, and while it hits the top and bottom gears, it has an 'empty' click that takes it from top gear to top gear and it skips from ring 3 to ring 5 with just one click.

I've read the response to How can I adjust index shifter so it doesn't skip the second chainring? but this is a 7 speed shifter (masquerading as an 8 speed and a 6 speed), not a 3 speed, so I don't believe the answer there applies here.

It seems that the twister is giving too much cable for each click (like a 6 speed shifter) and has its own position limiters which allow extra travel (like an 8 speed shifter). I've fiddled with the top and bottom limit screws on the derailleur, and with the [barrel] that simultaneously changes where ALL the indexes locate, but while I can get it somewhat aligned for all sprockets, it still does the 'not quite engaging properly' thing for a few of them, and I still have extra clicks at top and bottom.

How do I reduce the amount of cable each click gives? There's an intriguingly yellow 'c-deck plus' sticker on the twist-grip that looks like it's hiding a screw, and a couple of tiny Allen key looking things that I'm guessing are holding the unit together.


Update: the shifter declares itself to be a 7-speed shifter on the front, and the part number bit towards the back reads 'Shimano SL-RS43-7 Singapore 22.2' which mentions '7' so... presumably it's a 7-speed.

I don't know where to find the serial number of the rear cogset..?

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Hi can you give us part numbers if they are visible? This sounds very much like a miss-matched shifter / cassette combo to me. The pull ration differ between models, groups and manufacturers, especially with something like SRAM gripshift and old LX stuff for example. –  Mere Development Mar 14 '13 at 21:36
    
Are you sure that the cable is properly inserted into the shifter? –  Mladen Jablanović Jun 12 '13 at 16:02
    
It doesn't jiggle around - short of it obviously hanging out, how would I tell? –  android.weasel Jun 14 '13 at 9:20
    
You cannot reduce the amount of cable per click (at least not without a bulky converter gizmo). If the cable per click does not match the derailer then likely one of them has been replaced with an incompatible model. –  Daniel R Hicks Dec 1 '13 at 13:49

2 Answers 2

The Park Tool web site is generally the first place to go for info on how to do different bike repairs/adjustments.

But adjusting a derailer is fairly simple if you understand the basic principles.

First, you sorta ignore the shifter lever/handle and observe the derailer. On it are two "limit adjustments" -- a "low" and a "high". These are generally setscrews of a sort. One limits how far derailer can sift in the direction that the spring pulls it, while the other limits how far the cable can pull the derailer in the opposite direction.

You first need to get the cable slack (twist the cable "barrel adjuster" a bit if needed) and adjust the stop that the spring pushes against. This stop should be adjusted so that the derailer centers the cable over (usually) the smallest cog. Then use the shift lever/handle to get the cable tight and pull the derailer all the way in the other direction, against the other limit screw. Adjust that screw to position the derailer over the large cog. (You may need to adjust the shifter slightly as you make this adjustment, to keep the derailer tight against the limit screw.)

Only after adjusting the limit screws do you attempt to adjust the cable. If you're lucky simply adjusting the "barrel adjuster" in the cable will get everything working right, but it may be necessary to loosen the cable clamp at the derailer and slide more/less cable through it, if the barrel adjuster doesn't have enough range.

Having done all this you'd generally ride it around a bit, then go back and recheck all the adjustments, fine-tuning them.

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I agree- ignore the numbers on the shifter. Learn to look between your legs and check the position of the chain on the rear. Pretty soon, you won't even have to look to know what gear you're in. –  Steve H. Feb 8 '13 at 18:34
    
@SteveH. Well, you don't ignore the numbers on the shifter, necessarily. Once the limit screws are adjusted you adjust the cable so the gears line up. –  Daniel R Hicks Feb 9 '13 at 5:28
    
@DanielRHicks But that's not what I was asking: I said that I've already adjusted the limiters so the cable doesn't fall off at either end, and the cable slack: what I can't quite manage is to prevent one of the stops between the high and low gear from jumping between cogs: it's as if the gear shifter is actually a six speed, on a seven speed cog - except that it clicks eight times. I notice my question has missing bits - I'm not sure how that happened; I'll restore them as best I can. –  android.weasel Mar 13 '13 at 9:44
    
@android.weasel - It's possible the shifter or cable is sticking. Or you have the wrong shifter for your derailer & cluster. –  Daniel R Hicks Mar 13 '13 at 11:51
    
Did you actually answered the question? The question says that top and bottom limits are good adjusted, the gears are working good except of 1 or 2 of them. –  Alexander Dec 1 '13 at 4:51

It seems it was a combination of a worn chain (my fault) and defective shifter, the latter not much of a surprise given that the cycle came from Wheelies, who managed to fit this folding bicycle's seat post collar back to front so it couldn't be properly tightened in place without several times the rated force for the quick-release style bolt.

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