Vintage Dirt Bike Q & A

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PostPosted: Sun Sep 23, 2018 6:16 pm 
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Joined: Sun Sep 12, 2010 7:24 pm
Posts: 12
I have both a 1974 and a 1975 CR125; and both have the 520 chain conversions.

What is my best choice for the chain guide/ tensioner; for each bike. I could use either 1974 or 1975 swing-arms if I had to. I have parts to use either.

Any help appreciated, and Thank You in advance.

Stryke

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PostPosted: Fri Nov 02, 2018 3:13 pm 
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Joined: Sun Sep 12, 2010 7:24 pm
Posts: 12
Anybody??

What have you done on your CR125m and CR250M ?

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PostPosted: Mon Nov 12, 2018 11:11 pm 
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Joined: Sat Nov 03, 2007 11:33 pm
Posts: 21
Here's what I use for what it's worth.
I have a 74 CR125 and a 75 CR with a modified MR175 motor both running stock CR125 gears and 428 chain and stock suspension travel with no problems with excessive wear or stretched chains. With this setup I feel the 428 chain is more than adequate.
I also have a 76 CR125 with long travel suspension that needed to run a 520 chain setup with it's larger diameter rear sprocket to clear the swingarm pivot at full extension. I added a bracket made from a piece of angle iron bolted to the lower rear engine mount with a skate board wheel to support the chain and the stock rear chain guide on the swingarm.
To summarize, stock suspension travel use 428 chain and stock guide. Maintain it and keep it adjusted.
Long travel suspension may need 520 chain for clearance at swingarm pivot.
Hope this helps.
The 76 CR125 has been sitting in the garage for years so it's looking pretty crusty, so use the pictures for ideas and not to judge me on my bike maintenance.
Thanks,
Coll
Attachment:
File comment: 76 CR125 with stock chain guide on swingarm
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Attachment:
File comment: 76 CR125 with skate board wheel under swingarm pivot
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Attachment:
File comment: 76 CR125 with angle iron bracket on lower motor mount bolt
IMG_1968.jpeg
IMG_1968.jpeg [ 747.74 KiB | Viewed 22 times ]
[img]


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