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Got dem low down PO blues...sprocket/gearing question

Discussion in 'XJ Technical Chat' started by bigfitz52, Jul 12, 2008.

  1. bigfitz52

    bigfitz52 Well-Known Member Premium Member

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    81 Seca 550; I just discovered the PO replaced the 46T rear sprocket with a 45T, the front one is a 16T as it should be. Is this a common "mod" or just expediency (they probably didn't have a 46 where he got this...) and is one tooth going to affect final gearing enough to make an appreciable difference in acceleration and/or RPMs at speed? I found a NOS sprocket on eBay already but don't wan't to hassle with it unnecessarily. Opines?
     
    bigfitz52, Jul 12, 2008
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  2. MN-Maxims

    MN-Maxims St. Paul Minnesota

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    Don't think you would notice any change.
     
    MN-Maxims, Jul 12, 2008
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  3. chadwickm

    chadwickm Member

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    If it runs good, don't fix it. One tooth isn't going to make any noticeable difference.
     
    chadwickm, Jul 12, 2008
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  4. techyguru

    techyguru Member

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    thats about a 2% difference so at 4000 rpm before you will be at 4080 rpm. Probably not noticeable but you may want to change it next time.
     
    techyguru, Jul 12, 2008
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  5. dburnettesr

    dburnettesr Member

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    he would subtrack that 2% not add it the 45 rear tooth would lower the rpm not raise it..Dan
     
    dburnettesr, Jul 12, 2008
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  6. wizard

    wizard Active Member

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    I agree with techyguru, it will require higher RPM for the same road speed.
     
    wizard, Jul 12, 2008
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  7. Zookie400

    Zookie400 Active Member

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    no.....less teeth on the rear means less rpm for the same speed.
     
    Zookie400, Jul 13, 2008
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  8. flash1259

    flash1259 Member

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    I was told to add a tooth to the front gear or 3 to the rear to lower rpms for same speed . Glad i haven't done that yet.

    Will changing the gears to lower rpms harm the engine?

    other than losing the high rev what if anything could you gain/ lose by increasing / decreasing gear size??
     
    flash1259, Jul 13, 2008
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  9. wizard

    wizard Active Member

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    with the extra tooth.
     
    wizard, Jul 13, 2008
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  10. low-1-5-0

    low-1-5-0 Member

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    I done a sprocket change on my GSXR, went -1 in the front and +2 in the rear, there is a huge increase in low end acceleration and torque but I lost top end speed, almost feels that I lost 6th gear... 6th with the gear change feels like 5th without... but one tooth down in the rear isn't going to affect you... I would say that the only different you might get is a couple mph extra when the bike topped out, same you might get going down hill with the wind behind you :lol:
     
    low-1-5-0, Jul 14, 2008
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  11. mhhpartner

    mhhpartner Member

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    Fitz:

    Going from 16/46 to 16/45 changes the final drive ratio from 2.88 to 2.81 - about 2.4% (like the earlier posters said). This would cause the loss of a wee bit of acceleration, but would lower your cruising RPM by 100-150, which might save a sip of gas.

    However, I doubt that either the slower acceleration or higher gas mileage would be enough to be measurable/noticeable.

    Here is a site where you can download an Excel gearing calculator so you can play "what-if" to your heart's content!

    http://www.dropbears.com/u/utilities/gearing.htm

    Stay safe!
    Herb
     
    mhhpartner, Jul 14, 2008
    #11

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