1988 883 with 1200 conversion sprocket sizes?

Discussion in 'Sportster Models' started by kino45, Feb 17, 2012.

  1. kino45

    kino45 New Member

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    I have a 1988 883 sportster with a 1200 conversion.I need to replace my rear sprocket right now its a 48T and the front is a 21T now this is stock right? I get high RPMS at 60 and 70MPH some say put a 22T on with a 48T which will give me a 2.18 ratio now I have a 2.28 ratio I was wondering if I could use a 47T at the rear which with give me a 2.23 ratio which will reduce my RPMS some. I dont want to lose my off the line power I like to jackrabbit around town not on the highway much but when I am it screams at me. is this just a normal sportster operation and will it hurt my bike? should I just stick with the stock setup?


    thanks
     
  2. Rubyred

    Rubyred Senior Member

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    Info from a fellow rider, I don't if it will help you or not. Good luck.

    A smaller back or a bigger front sprocket will lower your RPM's while riding. Also remember that it's ratio's and a change of 2 teeth on the front is not the same as 2 on the back.

    Your factory ratio (48/21) is 2.29 (2.29 turns of the front to make the rear go around once)

    A 46/21 is a 2.19 ratio. (2.19 turns of the front to make the rear go around once)

    A 48/23 is a 2.09 ratio. (2.09 turns of the front to make the rear go around once)

    My '86 1100 has the same factory sprockets (48/21). At 55 mph it's running around 3400 RPM. I did some calculations (actually Microsoft Excel did the calc's) and the 46/21 would make 55 be around 3250 RPM on my bike. The 48/23 would be around 3100 RPM at 55 on my bike.


    Some things to remember. 1) Changing sprockets will require either adjusting the chain adjuster or changing chain length if the adjusters are at their limits. 2) getting lower RPM at highway will also lower RPM and power at the low end, like when you're pulling out from a stoplight. 3) Changing the front is a lot less expensive than changing the rear. And with the right tools, a lot easier too.
     
  3. kino45

    kino45 New Member

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    so best to just leave it stock? I have no tach so I go by sound I really like the stock setup for town running guess I just better leave it 21/48
     
  4. Rubyred

    Rubyred Senior Member

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    Based on what you want (low end power) I would leave it where it is. What are you looking for? Maybe some other mods will give you what you want.
     
    Last edited: Feb 17, 2012
  5. Dr. Dolittle

    Dr. Dolittle Experienced Member Staff Member Moderator Contributor

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    Since you stated that most of your riding was spirited, in town type and you're not on the highway much, I'd leave it stock.
     
  6. fin_676

    fin_676 Experienced Member Staff Member Moderator Contributor

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    As has been said leave the stock setup for quick acceleration from a stop

    Brian
     
  7. kino45

    kino45 New Member

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    all im looking to do is lower the RPMS down a bit when I do hit the highway thats why I figured a 47T instead of a 48T would about 5% I think? and still give me the off the line power my 21/48 is a 2.28 ratio a 21/47 would be a 2.23 ratio not a big change but enough to lower RPMS some and keep the torque
     
  8. gungatim

    gungatim Account Removed

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    I have a 22/49 combo on mine, and the acceleration difference is really not noticable, the highway cruising is alot nicer though. The 23 may require some grinding to fit under your sprocket cover, you will need to check. If it were me I would do the 22 and see how you like it.