KMC Missing Link won't close with KMC chain
 

So I just got a new KMC Z-72 chain and it comes with a Missing Link. Theoretically all you have to do is put the chain on, insert the Missing Link and close it, right? No. I can't get the link to close.

- No, I don't have a link tool.
- I can close the link to itself off the chain, by hand, easily.
- If I just put the link on one end of the chain only, I can't close the link.
- If I take the Missing Link from my old chain and put it (temporarily) on the new chain, I can just barely get it to close with a lot of force. On the old chain, I can take that same link on and off by hand without much force at all.
- I don't know what the old chain was other than a KMC Z-series for 7-speed, looking a lot like the new one. LBS said this is the replacement.

So my question is: how much force should I be using to close the new link (the one that came with the chain) with the new chain?

It seems like you're supposed to be able to line up each outer plate with the channel in the pin from the opposite plate by squeezing the two halves together. And that if you have to use force, it's because you're deforming the plate by squeezing the pin through the opening without lining up the channel, which is bad .. right? Or is that just how it goes?

Sure don't want to damage the link and have it fail (open or closed).

Just wondering how this goes for other people.

Hold rear tire and push pedal forwards with a snap and it will close

It doesn’t go, on KMC 6/7/8 speed chains I never use the missing link, just use a chain tool and push out a pin. At one time, had quite a collection of the missing links, finally tossed them all, realizing I’d never use them, even after I bought a link tool.
Tim

It shouldn't tale much force at all to close the master link. You just push both sides of the master link together and have a helper pull on both ends of the chain. It should snap together and be ready to use. One person alone can do it but it is easier if two people work together

Most modern chains have the pins slightly mushroomed at each end which makes reassembling the chain more difficult than it was with earlier chains. The only time I use a chain tool these days is to shorten a chain that is too long. There is a very useful tool to separate the master link once it has been closed. I struggled with nasty greasy chains before finding out about the tool. You can get it from a domestic eBay seller for under $10. Wish I had known about it much sooner.
https://cimg2.ibsrv.net/gimg/bikefor...3793ee6302.jpg

Two possibilities that I can think of.

First, you are not putting enough pressure on the link to close it. To do that, close the brakes, stand on the pedal, and the link should close.

Second, you have a bad Missing Link.This happened to me. One of the pins was not perpendicular to the link plate, like this:

https://cimg5.ibsrv.net/gimg/bikefor...5f61b6a0ce.jpgI was unable to close it, and had to use another connecting link, in this case, a SRAM Powerlink. If your connecting link is faulty, get another link.

I've only used conventional chains on 7 speed, but on KMC 10-speed when I have problems it's because the pin isn't all the way in. After inserting each part I twist it back a forth to make sure the pin is all the way in. You should be able to see the channel on the far side before mating the plates.

scott s.
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I use them on most of my bikes whether they be 6-7-8-9 or 10 speed and have not had one problem closing them. You could have ended up with a dud.

Be sure it's the correct Missing Link for that chain. The older Missing Links came in 7.1mm and 7.3mm to match the pin lengths of the various KMC chains from 5 to 8 speed. If it's mismatched it won't close properly and will probably bind. Check the KMC website for details.

Thanks y'all, great advice here.

I did end up getting it to latch by installing it on the bike, right hand applying rear brakes, left hand squeezing the plates together, left foot holding me up and right foot applying gentle forward pressure on the DS pedal. (Kind of an acrobatic act ...) I suppose it works better on the bike than doing it by hand in your lap because chain tension helps align all the parts.

Surprise ending: now my chain is skipping when on either of my two smallest cogs, which I take to mean time for a new cog stack and/or chain rings. I can't tell for sure where the skipping is happening, front or back. I don't see obvious wear (except for a couple teeth on the middle chain ring) but that may just be because I don't have a new cog stack in front of me for comparison. I put the old chain back on and yes the problem goes away so I'm not done yet.

But now it's been five days since my last real ride so today I'm just going to take my old chain as is and hit the road.

You now have a tight link, could be the missing one, if you jammed it, or it’s the wrong one, or any of the other links. Time for the chain tool either way. Tim

You mean because it's only jumping on the smallest cogs, i.e. the tightest radius turns which the chain is not fully bending for?

Yup! Watch where it jumps, then grab the chain at that link, you’ll feel it. Loosen that link with the chain tool, if it’s the missing link, Chuck it, the missing link that is, not the chain.
Tim

fyi if you don't already know this - to loosen a seized link you should apply light force back-and-forth perpendicular to the flat side of the chain plates.


I also had a hard time with a new KMC Missing Link recently - had to stand on the DS pedal and bounce a bit - probably should have tried to diagnose the problem, but my technique worked.

It's very possible that the chain skipping has nothing to do with the chain and everything to do with worn out cogs on the cassette

Happened to me a few months ago.

I had a chain break so I bought a new chain. Put the new chain on and it was skipping like crazy.

I didn't think the cogs were worn but darned if they weren't. Once they were pulled off the bike it was much more clear how worn they were and the tiny bit the old chain had worn with them made it a perfect fit for the worn gears. But the new chain which wasn't worn didn't sit right in the worn gears at all and skipped like crazy

Skipping in the smaller cogs may not indicate a worn cassette or freewheel. Those cogs usually get the least wear for most cyclists.

Some of the most likely reasons for skipping:

1. Mismatch between the quick link and chain. Check the pin lengths. You may need a fairly accurate gauge for this to distinguish between 7.1mm and 7.3mm.
2. Mismatch between chain and freewheel -- I'm guessing freewheel in this case since you mentioned 7-speed.

In the first case, any binding with a mismatched chain and quick link can cause skipping.

In the second case, some freewheels are picky about chains. In particular the Shimano MegaRange freewheels want narrow chains. The spacers between cogs on MegaRange freewheels are a little wider in diameter than some other freewheels. A new chain that's too wide, by a tiny fraction, will contact the spacers in the smallest cogs, causing it to climb out of the teeth and skip under pressure.

I haven't seen the second problem with Shimano 7-speed cassettes, only with their MegaRange freewheels, the kind with the big jump to a 32 tooth or larger granny gear. I haven't experienced it with SunRace freewheels or Shimano Tourney freewheels, but that may be because of a correct match between chain and freewheels.

So if your bike has a Shimano freewheel, be sure to use a chain marked "narrow" on the link plates. And the correct quick link.

I know that riders are 99% satisfied with KMC chains, but I had a problem with the first one I used. It had a bum Missing Link (see photo in post #5 above) and it skated over the position 2 cog on a 9sp system. I adjusted the indexing over and over, trying to get the skate to stop. It wouldn't skate in the work stand, only on the road.

I examined the cassette closely, no signs of wear. The KMC chain was not worn excessively either. I put on a new Shimano chain, and the skate is gone.

An argument for using the same brand chain as your cassette. But I used SRAM chains for years before the KMC, worked fine. Won't use KMC again.

To reiterate, I know most people have good luck with a KMC chain, but I didn't. Moving on!

I just want to close this out and thank everybody for the great and detailed suggestions.

In the end I had to replace the chain and rear cluster (freewheel) together. Also the cones, although that's not why it was skipping. Now it's shifting and working as it should, no more skipping.

One thing, I was never able to get a consistent measurement of width across the pins. Not sure why -- I was using calipers, but I never seemed to find the right spot and they never stabilized on a value. It's probably time to get that big magnifying glass to work under.

@canklecat: Not MegaRange in my case, just a 14-28 7 speed. That's good to know about MegaRange being picky, I hadn't heard that before.

Thanks again.

Sometimes they are tight for the first time. I use these kinds of links all the time and haven't had too many problems with them.

Yup, I have a Shimano 7-speed 14-28 MF TZ21 freewheel on my '93 Trek 5900 (not the original wheelset, shifters or most components). Good freewheel, works fine with a KMC Z-72 chain and correct Missing Link.

FWIW, KMC has revamped its catalog, renaming some chains and eliminating others, so it's a little harder now to find the equivalents of some chains we're used to under other model designations.

To look for a tight link. Pedal by hand backwards slowly.
Watch each link closely as it goes over the cog and through the pulleys.
If there's a tight link, you may notice it acting slightly different....rising up a bit instead of properly engaging.

...or just watch for the lower pulley to twitch