Sprocket change, yes or no!

Discussion in 'General Harley Davidson Topic' started by Tahoe Kid, Nov 28, 2013.

  1. Tahoe Kid

    Tahoe Kid Member

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    Happy turkey day to all!
    I have a 103 and am curios if their are any advantages to reducing the smaller sprocket and increasing the larger one. Most oblivious is the low end tourque and a little top end. Will this hurt the over all performance?

    TahoeKid
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  2. wannaride

    wannaride Active Member

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    Your rpm's will be higher at the same speed. So if you are running 70 mph now & you change the pulleys (depending on how many teeth & which one) and the engine is turning 3000 rpm's then your rpm's will go up (for example only, like I said earlier it depends on which pulley & how many teeth) to 3600 rpm's. So as far as top end, it only would help if you are geared to tall & the engine doesn't have the torque to keep pulling & the next lower gear is to high to go to. Hope this helps


    Toby
     
  3. Tahoe Kid

    Tahoe Kid Member

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    Toby! Thanks for the reply! Was thinking of 1 on the smaller and increasing 2 on the large one?? Doesn't sound like a good idea!
    Thanks
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  4. dbmg

    dbmg Experienced Member

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    And to add, not knowing what year the ride is. You may have issues with computer signals not being correct for said bike and check engine light with fault codes. So if more power is what you are looking for, a downshift is equivalent to gaining 10 HP.
     
  5. biscuit

    biscuit Junior Member

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    Would you like a different answer?

    Mine is a 96" T/C with a 'Thundermax with Autotune',SE slip-ons and an air filter added. I also have a set of S & S 583 cams fitted. I have long talked about and considered altering my gearing; but it was always in the 'too hard" basket.I have various posts on this theme over the years.

    In MY opinion and with MY 2008 6 speed,i consider it overgeared.Late last year i'd finally overcome my reticence on this matter and did a lot more research.
    My bike has a 32t front pulley and a 66t rear pulley as standard.I decided to adjust my gearing by going 9.28% SHORTER. I fitted an Andrews 30t front pulley(6.25% change) and an RC Components 68t rear(3.03% change).

    As mentioned this gives a 9 odd percent gearing change.The reason I went like this was that I knew I would be able to retain the standard drive belt;and as my bike has 8500 klms on it this was a worthwhile thing to do.My axle position is pretty much where it was before the change.(it went rearwards with the smaller front and forwards with the larger rear).
    Plus,i didn't think a 6% change was enough: particularly when I calculated out engine RPM's versus road speeds.

    Standard,my bike at 60kph(our town speed limits) runs 1955 RPM in 4th gear.Too low for 4th and too high for 3rd.A real pain---.
    Front pulley only raised RPM's to 2077 ; rear pulley only was 2013 RPM's and both-as I run now-raised them to 2136. A world of difference and do-able with my engine mods. Doesn't sound like much,but makes a great difference. MUCH more pleasant around town.

    On the open road at 100 kph revs were 2344 and now they're 2561.Again, a world of difference.As I rarely even ride at 100kph or beyond, the increased RPM's don't bother me.Fuel economy is pretty much exactly the same or even a little better.The most important thing as far as i'm concerned is that the bike is so much better to ride FOR ME.MY way of riding might not be like yours,but it is a worthy thing to do.

    With my Thundermax I was able to fiddle around with the speedo calibration numbers until I got my speedo reading correct.If you don't have a T/max I think a company called 'Speedohealer" makes a unit that you can fit to your bike to recalibrate the speedo.

    Also,there is or was,a pretty useful Transmission ratio,pulleys and speed conversion chart on "Andrews Products" web site.Or you can calculate it all out.

    You can send me a PM if you want to know any specifics.
     
  6. Nikko684

    Nikko684 Active Member

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    I think it's more a question of; do you possess the time and patience, as well as research skills to take this on? I know I don't! lol, so you won't find me changing my gearing in the near future haha.
     
  7. wannaride

    wannaride Active Member

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    Real life vs paper, I would use the real life. Sounds like biscuit has done close to what you wanted. 100 KPH = 62 MPH. Like I said before, sometimes gearing lower can help top end. If you feel that 6th is useless then that is an option. But you can always drop a gear or two to get what you want. After all, if you are riding at 65 MPH in 6th & crack the throttle you will more than likely be better off dropping down to 5th or even 4th depending how fast you want to get going. One pro to gearing down is that you might be geared so that you don't have to drop a gear on the roads that you travel. I dropped 4 teeth on the rear & left the front the same. But mine is a 1999 & the primary gearing is different than yours. For me with the cam that I run I am happy. I may have been happier with the way it ran before I did the gear change (I did them both at the same time). But I feel that the bike is as fast & I lowered the cruise rpm's. So what are you looking for. Take off speed & not have to down shift as much while cruising. Do you ever feel that you need another gear (that is why I did mine the way I did). Good luck

    Toby
     
  8. mdouglas71

    mdouglas71 Member

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    Advantage is you get a higher top speed. I think its a reasonable thing to do if you bike has a good amount of power and you need more highway speed flexibility. An example.. is the honda rebel. While the bike is okay, its top speed is like 65mph. You want to get it higher...you'll change out the sprocket.