Chain tensioner damage CT200U-EX

#1
I was servicing Patrick's CT200U-EX after our 20 mile ride yesterday and found the chain tensioner is badly scored by the chain. None of my bikes have this device and the bike has 50 mile total on it. I did notice this last Monday after our ride but it was nowhere near as bad as this is. I see no reason for this to happen as the bearing is free to turn and the chain rides flat on the pulley. The chain is still new and has no wear that can be seen or felt. The device has only slight end-to-end play.
Any ideas? Crap part? Get rid of it?
chain tensioner.jpg
 

SAS289

Well-Known Member
#3
If you take the clip off to remove the bearings was the shaft completely rusted? Both of mine were when the bikes were brand new. Had a time cleaning off the corrosion in order to get the inner bearing out. And I had to tweak mine so the chain rode flat on the pully. They do wear pretty quickly.
 

SAS289

Well-Known Member
#5
It may rotate freely by hand but drag at higher rpm, maybe...

I'd replace the roller with a large (OD & width) skateboard wheel.

https://www.oldminibikes.com/forum/index.php?threads/chain-tensioner-help.169787/

View attachment 267363
I looked at this idea a few years ago and it is a good one. As long as the roller you use is near the size of the original. Too large adds unwanted spring tension. 1/4-3/8" larger in diameter than the original would be ideal IMO.

One guy on Youtube runs his Coleman's jackshaft without the pivot and roller. lol.
 
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#6
I looked at this idea a few years ago and it is a good one. As long as the roller you use is near the size of the original. Too large adds unwanted spring tension. 1/4-3/8" larger in diameter than the original would be ideal IMO.
Certain applications might limit how large you could go. I suggest wide for the obvious reason that the wider the roller the less likely for the chain to drop off the edge. I suggest large OD because the roller would spin at a lower rpm than a smaller one (easier on the bearings); it would be easier for the chain to spin a larger roller due to increased mechanical advantage/leverage combined with greater contact area, making it less likely for the chain to slip on the roller (less wear); it could also be slightly easier on the chain due to larger bend radius.
 

SAS289

Well-Known Member
#8
There was a recent thread on a chain roller for a different bike. Some guy had a way to trim down the large skate board wheel to a much better size. What he did looked like work of art. Can't remember how he trimmed it down but it was perfect.
 
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