Steve Whitlatch 

I purchased an almost brand new looking freewheel from the LBS $5 bin to replace a broken one on a bike I am trying to flip. The chain jumps on the lowest cog. I tried it on another bike and the same thing happens. I looked it over and see nothing out of the ordinary with the teeth. What should I be looking for and can I file down anything to make it stop jumping?

jacksbike

Sounds to me that the smallest cog , most likely 14 teeth, is worn out. If the chain jumps all of the time on the smallest, even on another bike with a different chain, this is most likely the problem. Freewheel is shot -you need a new one.

cny-bikeman

It's not a good idea to use "lowest" and "highest," when referring to cog or gears, as people sometimes mean different things. Is it the smallest cog or the largest? If the smallest (actually the one engaged in high gear) then it's worn enough to not mesh properly with a new chain, and must be replaced. One cannot always see the wear on a cog until it is fairly extreme. You would need to determine the brand and model of freewheel to know whether just the cog can be replaced.

fietsbob

Clearest is to say how many teeth it has .. does require counting them..

Steve Whitlatch 

Yes it is the smallest 14 tooth. So much for picking the best looking one in the box. It just jumps on one tooth.

FBinNY 

Plate width varies among chains. This is a non-standard dimension because the plates don't actually run on anything. I can't tell for sure but your chain seems to have plates near the wide end of the range.

It's possible that the plates are touching the flange at the base of the smallest sprocket.

It's easy enough to check, shift to the sprocket and look.

Steve Whitlatch 

It looks like it is touching. The freewheel that came with the bike was bad. Would not spin right. It did not have hyper glide ladders on it like this one I put on. The chain is old and so is the chain on the other bike I tested this wheel on. The bike is a woman`s Raleigh Record, late 80`s early 90`s Taiwan. It came with Suntour Accushift 2000 RD and shifters so it is indexed shifting. I have no idea if this was an original shifting setup or an add on? I paid $10 for the bike. Would a new chain help?

FBinNY 

So, there's the problem. The cure is simple enough -- a more modern chain. Modern chains have smaller plates that overhang the rollers less, which improves shifting on index systems.

Steve Whitlatch 

Thanks for the help. I will buy a new chain tomorrow and let you know if it works.

FBinNY 

Be sure to open the box and look at the chain. You want one where the plates don't extend fa beyond the roller diameter. (if at all).

Steve Whitlatch 

The bike Shop I was going to get one from has Sram 8 speed chains just like this one I put on this Univega. Will that work?

fietsbob

If you are putting a new chain on an old freewheel with some cogs worn more than others ,

you may wish you bought a new freewheel too..

Bill Kapaun

Note the chart and the cog spacing for Accushift.
https://sheldonbrown.com/cribsheet-spacing.html
It appears your RDER moves 5.5mm per shift while you probably have 5.0mm cog spacing?

cny-bikeman

Yes. https://en.wikibooks.org/wiki/Bicycle...ns/Chain_sizes
Sheldonbrown.com also discusses chains in detail.

The index issue has nothing to do with a problem with the small cog, as the cable is under essentially no tension at that point. The outer limit screw determines the derailleur position. As noted, though, the indexing may not work correctly with a freewheel that does not have the correct spacing for Accushift.

If you are going to be flipping bikes it would be a good idea to educate yourself further. Some potential mistakes can be unsafe for those who purchase the result of your labor.

FBinNY 

FWIW- if the issue were index spacing related the OP would be reporting issues in most gears. He reported problems ONLY in high, then later confirmed that the chain plate was touching the lockring as I suggested. This is analogous to the issue of using standard l12t lockrings with 11t cassettes,

Ideally he should look for a slightly wider chain, but there's no reason why the 8s chain wouldn't work as long as the plates weren't much wider than the rollers.

Bill Kapaun

It "appears" to be a 6 speed free wheel.
Assuming the RDER was set to engage the largest cog "somewhat correctly", 5 shifts would result in the RDER being off by 2.5mm or 1/2 cog by the time it reached the last cog, assuming my Shimano Free wheel-Accushift premise.
It may be set up so that on the largest cog, it is slightly over shifted toward the spokes. That would result in "quiet" running for the 1st up shift or 2 and then increasing chain noise as it is shifted to the smaller cogs.
Just because the OP didn't report problems in the other gears doesn't mean they aren't happening.

It's up to the OP to clarify if ALL the other cogs run "perfectly" or if things get worse through out the gear range.

FBinNY 

Anything might be possible, but spacing problems are progressive, so while it would skip badly on the 1's sprocket, it would also skip slightly on the 2nd.

This is a case of looking for horses, not zebras when you hear hoofbeats (in the USA). While people often mis-describe problems, you need to start by taking them st face value. If someone reports a problem affecting ONLY 1 sprocket, start by seeing what may be different about that 1 sprocket, and a theory consistent with that. Then, if there's no good theory that fits, you can move down to more complex theories.

Of course, it's possible that once the OP resolves this specific problem, he'll still find he has poor shifting due to incorrect spacing.

Steve Whitlatch 

The new chain did the trick. The bike shifts like new. Fast, quiet, and smooth as can be in all gears. Thanks for the help.

Steve Whitlatch 

I am educating myself with each and every bike I do. I did not sell the bike yet did I ? I will never sell a bike that does not work like new. I am not afraid to ask questions either.