Chain loose then tight

Discussion in 'Welcome to the World of Motorized Bicycles' started by Baby man, Sep 2, 2017.

  1. Baby man

    Baby man New Member

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    So i got myself a new hyper bicycle with a new 66/80cc motor. After awhile of riding I felt that my chain had fully stretched so i tried to tighten it up again. While tightening I found that the slack of the chain would change to loose and then tight when I would spin the wheel so I figured something was out of alignment. After trying to re-align the motor, sproket, and back wheel I have had no luck. Everything looks straight although the chain still gets super tight and then extremely loose when I disengage the clutch and just roll it in a straight line. I know this still must be my alignment but i am extremely frustrated as I thought this would be a quick fix. Any tricks you found to making sure that everything is aligned properly because this is SUPER annoying. Thanks -Baby Man
     
  2. Chaz

    Chaz Active Member

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    If I understand the issue correctly I would say you should check the rear sprocket to see if it is centered.
     
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  3. signet

    signet New Member

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    You likely have some runout on the rear sprocket... Try taking off the drive chain and then get the rear wheel turning fast enough to observe the rear sprocket as it turns... If you have the rag joint version, it should be an easy fix... Just mess with it until it centers up... If you have the CNC machined version rear sprocket, you'll have to loosen the countersink allen-head machine screws, then try to rotate the sprocket into different bolt positions, then tighten and retighten until it centers up better...

    Don't expect it to be perfect... Incidentally, the best thing to do if you still have runout is to get a spring type chain tensioner... This type of unit will constantly readjust itself in real time as you run your bike...
     
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  4. Baby man

    Baby man New Member

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    Thanks for the quick replies guys. I am going to try to re adjust my rear drive sproket and let you know how it goes
     
  5. Tony01

    Tony01 Active Member

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    Definitely rear sprocket. It doesn't take much runout for a chain to go slack. Talkin a 1/32" will be way too much. Really the only good way to mount those is when the center hole is a little bit bigger than a diameter on the hub somewhere. My sprocket has a 1.405" ID which is .030" bigger than a freewheel thread, so I mounted it on the freewheel threads and used 6 layers of coke can to shim it. Typical cheap hubs will have a freewheel sized casting on the other side of the hub that can make this possible. Good luck.
     
  6. allen standley

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  7. allen standley

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    No no ...nope. Get your sprocket as centered and true as possible. I never use the kit supplied tensioners and use spring loaded tensioners only when absolutely necessary. Get your sprocket correct. I do agree Signet to mess with it til it centers up, But Spring tensioner will not be the answer in this situation.Go to my happy chains album for tips and suggestions.
     
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  8. Baby man

    Baby man New Member

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    So I have gotten all the way to the point of getting a torque wrench to tighten up my back drive sprocket and rim to make sure it is perfectly center and aligned yet I still have problems with the chain being tight and loose as I roll the bike. I like the idea of replacing the rag joint with the metal adapter as Allen Standley recommended although that is too expensive for me being that it is like $80. How do you guys not have this issue like I do!? I can understand it being a tiny bit different in slack as I roll it but not as bad as it is being that the chain changes within a few inches of slack all in one rotation of the the tire.
     
    #8 Baby man, Sep 26, 2017
    Last edited: Sep 26, 2017
  9. Baby man

    Baby man New Member

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    By the way if you are curious as to what bike I am using it is the one in my profile picture if that helps.
     
  10. Jroge1523

    Jroge1523 New Member

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    your rear sprocket probably has a hop in it. What I do to get my sprocket aligned. Is first make sure the rubber discs have the same thickness all the way around then I get all my bolts and nuts ready to be tightened down stick my finger over each nut and tighten the bolt until the tip touches my finger and do that with all of them. Then I go around and do three full 360 degree turns on each nut in a star pattern and I make sure my sprocket is Center and then I repeat the process but only do one and a half turns until the rubber is bent over the spokes. If you do that and your sprocket is still not aligned. You need new rubber rag joint because rubber wasnt cut evenly from the factory.
     
    #10 Jroge1523, Nov 7, 2017
    Last edited: Nov 7, 2017
  11. Dan

    Dan Staff
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    Before mounting a sprocket, I take a file and knock any bits down on each tooth. One knobby can mess with ya..


    Just how I center rear sprocket. Center it perfectly. Then walk the bike and watch for "lose, tight lose...." and tap to perfection with mallet, price of wood or really gently with a hammer.

    Sprocket not centered really sounds like the problem/answer. I wouldn't spend any money before addressing this.

    Or am I late and ya got it worked out?
     

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