trouble with rear sprocket/chain

brucemg51

New Member
Jul 10, 2008
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I've spent the better part of a day aligning the chain with the front and rear sprockets and making sure the chain isn't rubbing on the frame or tire. But, the chain doesn't seem to want to mesh smoothly with the rear sprocket. It keeps binding up and coming off the sprocket. It makes a lot of noise even when it does manage to stay on for a while. Any hints as to how to smooth it out?
 

Bikeguy Joe

Godfather of Motorized Bicycles
Jan 8, 2008
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up north now
See if the tips of the teeth are catching the chain. Some older kits had this problem. The way around it is to take the rear sprocket off and file or dremel the edges of the teeth off. Not a big deal.
 

brucemg51

New Member
Jul 10, 2008
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See if the tips of the teeth are catching the chain. Some older kits had this problem. The way around it is to take the rear sprocket off and file or dremel the edges of the teeth off. Not a big deal.
Not sure what you mean. Is catching the chain a good thing or a bad thing? File the edges of the teeth so they are narrower?
 

NunyaBidness

Active Member
Jun 29, 2008
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memphis tn
Not sure what you mean. Is catching the chain a good thing or a bad thing? File the edges of the teeth so they are narrower?
yeah, just knock the square edges of the teeth off, on both side, and this will allow the chain to meet the sprocket better
good luck
 

jasonh

New Member
Jun 23, 2008
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Here's one thing I noticed today. If your rear chainstay is angled outwards as it goes back towards the wheel, you may have issues. The tensioner will be at the same angle of the chainstay, and this makes the chain run at an angle across the tensioner wheel. If you adjust it so it's quiet, it takes the chain off the sprocket.

One solution would be to "twist" the bracket. I tried to do it with a couple pair of pliers today but failed. Need to figure out a good way to do it.
 

Andyinchville1

Manufacturer/Dealer
Dec 26, 2007
502
1
18
Scottsville, VA
HI jasonh,

To bend the tensioner bracket it really helps to have a table mounted vise and a large pipe wrench and/or a small sledge hammer....Pliers may work but you'd probably have to look like Rambo to do it using that ;-)

Hope this helps you....Good luck!

Andrew

PS - 2 pipe wrenches may work tho....just need the longer ones for more leverage....
 

Bikeguy Joe

Godfather of Motorized Bicycles
Jan 8, 2008
11,843
235
63
up north now
Here's one thing I noticed today. If your rear chainstay is angled outwards as it goes back towards the wheel, you may have issues. The tensioner will be at the same angle of the chainstay, and this makes the chain run at an angle across the tensioner wheel. If you adjust it so it's quiet, it takes the chain off the sprocket.

One solution would be to "twist" the bracket. I tried to do it with a couple pair of pliers today but failed. Need to figure out a good way to do it.

I "adjust" mine with a pair of 18" channel lock pliers.
 

brucemg51

New Member
Jul 10, 2008
157
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Here's one thing I noticed today. If your rear chainstay is angled outwards as it goes back towards the wheel, you may have issues. The tensioner will be at the same angle of the chainstay, and this makes the chain run at an angle across the tensioner wheel. If you adjust it so it's quiet, it takes the chain off the sprocket.

One solution would be to "twist" the bracket. I tried to do it with a couple pair of pliers today but failed. Need to figure out a good way to do it.
What is "rear chainstay"? Is this different from the tensioner? Am I missing something?
 

Andyinchville1

Manufacturer/Dealer
Dec 26, 2007
502
1
18
Scottsville, VA
Hi,

The rear chain stay is the piece of the frame that you typically mount the chain tensioner on....It is the tube that runs parallel to the ground from the bottom bracket to where the rear wheel attaches to the frame.

Hope this helps

Andrew
 

brucemg51

New Member
Jul 10, 2008
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Hi,

The rear chain stay is the piece of the frame that you typically mount the chain tensioner on....It is the tube that runs parallel to the ground from the bottom bracket to where the rear wheel attaches to the frame.

Hope this helps

Andrew
Thanks. Being an old motorcycle mechanic, I would think of that piece as the swingarm, although the term doesn't really apply to a bicycle.
 

Venice Motor Bikes

Custom Builder / Dealer/Los Angeles
Mar 20, 2008
6,609
416
83
Los Angeles, CA.
I've spent the better part of a day aligning the chain with the front and rear sprockets and making sure the chain isn't rubbing on the frame or tire. But, the chain doesn't seem to want to mesh smoothly with the rear sprocket. It keeps binding up and coming off the sprocket. It makes a lot of noise even when it does manage to stay on for a while. Any hints as to how to smooth it out?
You should mount the rear sprocket the way the factory designed it! (don't try to change things around.)
The tire will be fine if the chain rubs it a little... if it really bothers you, you can put on a smaller tire.
& last... bend the chain tensioner however it takes to where it feeds the chain nice & straight onto the rear sprocket!
 

brucemg51

New Member
Jul 10, 2008
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You should mount the rear sprocket the way the factory designed it! (don't try to change things around.)
The tire will be fine if the chain rubs it a little... if it really bothers you, you can put on a smaller tire.
& last... bend the chain tensioner however it takes to where it feeds the chain nice & straight onto the rear sprocket!
I have mounted the sprocket according to directions. At first, I thought the problem was that the chain was rubbing against something, but then I realized that it's the chain not meeting with the sprocket the way it should that is the problem. I'm going to file the sprocket teeth and see if that helps.
 

Venice Motor Bikes

Custom Builder / Dealer/Los Angeles
Mar 20, 2008
6,609
416
83
Los Angeles, CA.
I have mounted the sprocket according to directions. At first, I thought the problem was that the chain was rubbing against something, but then I realized that it's the chain not meeting with the sprocket the way it should that is the problem. I'm going to file the sprocket teeth and see if that helps.
The last sentence of that post is the most important for your chain problem...
Make sure the tentioner is feeding the chain onto the sprocket PERFECTLY. (bend it if you have to!)
 

brucemg51

New Member
Jul 10, 2008
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I've filed the sprocket teeth and it definitely is better although still noisy. I'm hoping that will quiet down as the bike is broken in.
 

brucemg51

New Member
Jul 10, 2008
157
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0
I've filed the sprocket teeth and it definitely is better although still noisy. I'm hoping that will quiet down as the bike is broken in.
Nope. Still no good. I can see what's going on here. No matter how I align everything, the idler wheel keeps pushing the chain off the sprocket. This is my second build and I had no of this problem before. I'm thinking I'm going to try to bend open the rear fork a bit, so I'll have more room to work back there, but I don't know if that will help. Four times now, I've had to drag the bike back to the shop with a seized rear wheel.
 

jasonh

New Member
Jun 23, 2008
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Bend the rear fork of the bike frame? Please don't do that. Just bend the tensioner.

I wish I had a vice, so I could bend mine.
 

brucemg51

New Member
Jul 10, 2008
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Bend the rear fork of the bike frame? Please don't do that. Just bend the tensioner.

I wish I had a vice, so I could bend mine.
Why not bend the fork a little to open it. I've done that before. I'm talking about a few mms.

Buy a vice. Good solid workbench with a vice is the most important equipment for any mechanic.
 

jasonh

New Member
Jun 23, 2008
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I just wouldn't bend the frame of the bike if you can avoid it. Sometimes small tweaks to the frame can cause big issues.
 

brucemg51

New Member
Jul 10, 2008
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Looks like I won't have to bend the frame at all. The problem was that the bolts holding the tensioner to the frame were stripped so I couldn't keep them tight. Every time they'd loosen up, the tensioner moved and caused the chain to leave the sprocket.