Where On The Swing Arm Should I Measure For Proper Chain Slack?
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Thread: Where On The Swing Arm Should I Measure For Proper Chain Slack?

  1. #1
    Junior Member ATTHECROSS's Avatar
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    Where On The Swing Arm Should I Measure For Proper Chain Slack?

    Hello Everyone!

    Merry Christmas! The chain jumped off the rear sprocket of my TW. It was a bummer because it scuffed up some of the swing arm, etc. After it happened I noticed that the rear axle adjustment plate was set to different indicating numbers on each side. The drum brake side it was set to "3" while the chain side was set to "2". That is the only reason I can assume it jumped. But my question is, where is the correct spot on the swing arm that I should measure for chain slack at? If anyone can provide a picture that would be much appreciated. The Yamaha owners manual does not show specifically where I should measure at. I have attached the manual image to this post. Also I know what the manual recommends for chain slack. Is there any specific measurements that you all prefer? Thanks for the help in advance. I don't want this to happen again. IMG_0816.PNG
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    Senior Member Dryden-Tdub's Avatar
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    The simple answer is, as close to midway between the front and rear sprocket as possible. Remember that you are not building a Swiss watch. Close is close enough.



    Tom
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    Senior Member Howsbentley's Avatar
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    Where On The Swing Arm Should I Measure For Proper Chain Slack?

    Here’s a good visual reference -



    #GYG
    '13 TW200

    A.T.
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  5. #4
    Junior Member ATTHECROSS's Avatar
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    Thank you both! I will definitely check out the video ASAP! Much appreciate the help! Take care!
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    Senior Member elime's Avatar
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    A little to loose is much much better than a little to tight.
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    Long live the internal combustion engine!

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    Junior Member ATTHECROSS's Avatar
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    Thanks for the advice elime.
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    Senior Member grewen's Avatar
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    3 on one side and 2 on the other is a huge difference!! how did it get that far out? i have never really measured with anything other than my toe. with the snails, the chain is going to be either too tight or what is going to look like too loose, and like Elime says, too loose is the better of the two
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    Greg

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  9. #8
    Senior Member elime's Avatar
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    The chain is tightest when the front sprocket drive shaft, the swing arm pivot bolt, and the rear axle are in a straight line. Adjust your chain when this happens. When not in a straight line, as it is in the picture, the chain will be looser. Don't worry about it being to loose as long it is not to tight when those three points line up.
    P6040026.JPG
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  10. #9
    Senior Member RockyTFS's Avatar
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    Quote Originally Posted by grewen View Post
    3 on one side and 2 on the other is a huge difference!! how did it get that far out? i have never really measured with anything other than my toe. with the snails, the chain is going to be either too tight or what is going to look like too loose, and like Elime says, too loose is the better of the two
    BOTH of my TW's need exactly that much differential to have the axle parallel to the swing arm hinge bolt! This is apparently quite common, and the only way to be certain that the axle and swing arm hinge are parallel is to measure the center to center distance from swing arm bolt to axle bolt on both sides. It doesn't matter what the value is, just that they are equal.

    The way I found this out was when I installed the dual sprocket and noted that the outside of the OEM sprocket was worn a lot and the inside not at all. There is a photo of the OEM sprocket wear on my post on page 8 of the Dual Sprocket sticky. There was NO indication in handling that it wasn't OK, and I imagine that 98% of the TW's live out their lives with non parallel axles. Not mine.... My right side snail has to be three notches less than the left side, which is 3 to 2, 8 to 7, 4+1 to 3+1, or whatever.

    Want to find out? Take any piece of wire, make a sharp 90 degree bend in one end, center that on the axle bolt and put your thumbnail on the other end at center of the swing arm bolt. Make a mark with needlenoses or marker, then transfer to the other side and remeasure. Do it several times. On the right side you have to sneak the wire behind the rear brake mechanism to avoid too much of a bend throwing off the measurement. I figured it was an anomaly until I measured the brand new 2018 and it was exactly the same off.

    Rear sprocket wear at 11,000 miles was equal on both sides. That tells me the rear tire and axle are running exactly perpendicular to the chain, and the sprocket is perfectly lined up with the chain, like they should be.

    Oh, and I usually set my slack at between 1.5 and 2 inches and don't worry about it until it gets to be more than 2.4 inches. You will feel a bit of jerkiness on the lower gear shifts at that value.
    Last edited by RockyTFS; 12-25-2017 at 03:56 PM.
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  11. #10
    Senior Member elime's Avatar
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    Very interesting. A quick check with a piece of coat hanger wire and both my TW's were nearly equal on both sides. not exact but almost.

    I did notice when I had dual sprockets one side of the sprocket was worn heavily but I figured that was to chain misalignment.

    How would one check the engine sprocket to the rear wheel sprocket? Any ideas?

    One thing I do is make the axle nut "snug", then I take a piece of wood and place it against the axle and tap it with a hammer driving the axle forward so the snail is tight against the pin, then I torque the axle nut to spec. It often looks fine but with the tap of the hammer I can see it move forward. This happens every time I R&R the rear wheel.
    Last edited by elime; 12-26-2017 at 10:23 AM.
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