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  1. #1

    Join Date
    Jul 2013
    Posts
    15

    Default Rear wheel alignment issue. 80 sportster.

    So I was trying to get the rear wheel all dialed in this weekend. I used square box tubing across the front and rear sprockets to get the sprockets lined up. Now my problem is that my wheel needs to shift over 5/8Ē to be centered and to allow for my rear caliper mount. So Iím thinking that Iím going to need an offset front sprocket. Does that sound correct? The rim I have is a brand new tc broís 16x3. Also I still have the slightest bind at the front sprocket. Could this just be from and old worn out front sprocket. I donít know if this helps but the front sprocket is 21 tooth and the rear is 48 tooth the bike is a 1980 sportster. Never thought mounting the rear wheel would be this much of a pain ha ha ha.

  2. #2

    Join Date
    Jul 2013
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    15

    Default

    Click image for larger version. 

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    Sorry for the blurry pic

  3. #3

    Join Date
    Dec 2018
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    Default

    I have straightened out many home builds for customers over the years, and the rear wheel set-up is usually the problem. Chain line, centering, wheel alignment, and space for the brake all have to come together for success. You must consider ALL facets. I start with wheel alignment. If the wheel is not straight in the chassis, you can't set the chain line or even assure that the wheel is centered (or off center, and by how much).

    On an '80 XL with a modern wheel, you will need a flat sprocket, and the wheel should be on or very near centerline when sprockets are aligned. There is very little room for the caliper bracket in a swingarm, and that is probably true for hardtail sections as well.

    You may have to back up and check to see if your frame is straight.

    Jim

  4. #4

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    Dec 2018
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    Default

    Ah! Pics.

    Ditch that dished sprocket.

    Jim

  5. #5

    Join Date
    Jul 2013
    Posts
    15

    Default

    JBinNC.
    I’m assuming your talking about getting rid of the dished rear sprocket. When I centered the wheel first I had room on the left side for my caliper mount but on my sprocket side my rear sprocket stuck out 6/32 of an inch past the front. Do you happen to know of a place to get a flat rear sprocket? Is there a way to check frame alignment with out a jig? Also wanted to say thanks for the help.

  6. #6

    Join Date
    Dec 2018
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    The flat sprocket you need is for about a '90 model XL (right before they went to the belt). I'll try to remember to get you a part # later. The dished sprocket you have is correct for your '80 XL, BUT ONLY if you are using the original rear wheel.

    The way I check that the rear wheel is square in the chassis, when working on a table:
    Level the table left to right.
    Level the bike left to right. Use a level on the bottom frame tubes.
    With a machinist's square, mark the table with the lower frame rail locations. Draw lines (should be parallel).
    Use a straightedge on the wheel (or tire) and align the wheel with the drawn lines.
    Then you can move it right or left to center it, or install it offset a little to get the chain line right.

    Jim

  7. #7

    Join Date
    Jul 2013
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    Default

    Ok awesome. Sounds easy enough. I’ll give it a try tonite.

  8. #8

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    Dec 2018
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    C,

    A 48T flat rear sprocket can be had from Drag Specialties, part # DS-325354. It is equivalent to HD part # 41470-86 according to my notes.

    Jim

  9. #9
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    Dec 2017
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  10. #10

    Join Date
    Jul 2013
    Posts
    15

    Default

    JBinNC
    I finally got the flat sprocket in and I mocked every thing up and I went from 5/8” off to about 1/16” off and was able to fit my brake caliper mount in. The front and rear sprocket are lined up almost perfect I would have to add 1/32” spacer to the front sprocket to be 100% lined up sprocket to sprocket. Do you think the the wheel being 1/16 off would be a problem?

  11. #11

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    Dec 2018
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    No, the wheel can be a little out of center with no issues. If it's a wire wheel, once you have the hub in the right place to make the chain line right, you can adjust the spokes to get the rim centered in the chassis.
    FYI, all swingarm big twins have the rear wheel offset to the left. As far as I know, all XLs have the rear wheel centered.

    Jim

  12. #12

    Join Date
    Jul 2013
    Posts
    15

    Default

    that’s great to hear. When I get the rear tire mounted I’ll have them adjust the spokes to make up that 16th of an inch. I appreciate all the help. Now to tackle the front end.

  13. #13

    Join Date
    Dec 2018
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    Default

    Do the spokes before the tire is mounted. But, I would not worry about 1/16". Just get the chain line as close as you can, and run it.

    Jim

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