Sprocket sizes for 2007 Ninja 650

Discussion in 'Technical Forum' started by Nevets, Aug 17, 2016.

  1. Nevets

    Nevets EMRA Executive Member

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    Steve O'Brien
    I'm going to install a new chain and sprockets for next year, and I'm looking for suggestions about what size of sprockets to install.

    My Ninja 650 comes stock with 15 in front, and 46 at the rear. I currently have 14 in front, and 46 at the rear.

    I'm happy with the 14 on the front.
    I want to go bigger on the rear, but I'm not sure how big. I'm thinking at least 48. Has anyone else experimented with this? Is there a limit to how big I can go? Is 50 or 52 just ridiculous?
     
  2. Beatinpileguy

    Beatinpileguy Member

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    I raced an 06 and here is my findings 14 front 46 rear.

    That bike has a great mid punch so I am not sure why you would sacrifice straight line speed for more acceleration out of the turns? I also found that I could carry more corner speed then most others on the 600's and 1000's. I would get killed on the front and back straights. Just a thought. your already at a disadvantage in power, IMO going bigger out back will make it worse.
     
  3. Nevets

    Nevets EMRA Executive Member

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    Hi Chris,

    Thank you for replying.
    I guess I'm a little bit confused about what you're saying though. Why would going to a larger sprocket sacrifice straight line speed? You even state that it would result in better acceleration out of the turns. I understand that I will have to do more shifting with the larger rear sprocket, but since I never touch 5th or 6th gear with my current setup, won't that increased acceleration result in higher speeds in the straights?

    I don't understand how a larger sprocket on the rear can make the power disadvantage worse.

    Any elaboration/explanation you can offer is appreciated.
     
  4. blam

    blam Administrator

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    think about a mountain bike Steven.

    in first gear, you are on the small front sprocket and small rear sprocket. you will be able to go much faster, but its harder to pedal/accelerate (more pedal resistance).

    when you change gear and put the rear set to the larger sprocket, what happens? much easier to pedal quickly and accelerate however, you will be pedaling much faster to achieve the same speed as if you were on the small rear sprocket.

    it all has to do with gear ratios
     
  5. Nevets

    Nevets EMRA Executive Member

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    Hi Brian,

    I guess this is exactly why I want to go to a larger gear on the rear tire in the first place.
    Currently, I never use 5th or 6th gear (and 4th very little).
    With a larger sprocket at my back tire, the engine would be able to accelerate at a higher rate. Once I hit my redline, I'll have to shift up to the next gear, but then I'll still be able to accelerate faster in that gear as well, thanks to the larger sprocket.

    To bring it back to your mountain bike example, with the larger sprocket on the rear, it will be easier to pedal to speed up. Once my legs start moving too fast, then I can shift up a gear in the transmission.

    So my understanding is that with a larger gear on the rear tire, the drawbacks are:
    • Having to shift gears a lot more
      A lower top speed

    I'm okay learning to shift more.
    And I can never reach my top speed anyway, because my bike doesn't accelerate fast enough to reach it at Castrol.

    I'm open to anything that I might have missed, if anyone has anything to add.
     
  6. Bongo

    Bongo New Member

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    Mitch
    You have a solid understanding of the concepts. Go to gearingcommander.com, load up the gearing for your bike and play around. You can get an idea of rpm to speed relationships and see what you'd like to do.
    Do you have a slipper clutch and quick shifter? Shifting more is more work load and without these will be even more. You may have to strike a balance between max drive/ideal gearing and rideability. Just some thoughts.
     
  7. Nevets

    Nevets EMRA Executive Member

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    Thanks Mitch,
    I do have a slipper clutch, but no quick shifter.
    I'll play around on that site and see what looks good.

    It sounds like the real limiting factor for max size on my rear sprocket is how far it drags down my top speed.

    Thanks again everyone for the help.
     
  8. blam

    blam Administrator

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    BINGO, Bongo.

    less work and thinking needed on the track = speed
     
  9. electrobiker86

    electrobiker86 Active Member

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    Wondering how the sprocket change went for you, looking at changing my rear sprocket as well.
     
  10. Nevets

    Nevets EMRA Executive Member

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    When I bought the bike, it had a 14T front, and 46T rear.

    I tried out the 48T rear, and I instantly hated it.
    All my shift points were way off. I only completed 2 sessions with the new gearing before I switched back. I found that I was running into the redline during corner exit, which meant I couldn't get on the gas when I wanted to because I had to shift first. This was especially true in corner 3, 4, 11, and even 14 though I think I just needed to get use to the new gear for the chicane. Before the change, I could get on the gas at corner exit, and then quickly shift at the beginning of the straight.

    I am holding onto the larger sprocket though. As I get faster, and my shift points change with improved rider skill, I might try it again later.
     
  11. electrobiker86

    electrobiker86 Active Member

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    I was contemplating dropping the rear size in hopes of being able to stay in 2nd gear more.
     
  12. Racin Jason

    Racin Jason Member

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    One thing to keep in mind. Engine braking. A bigger sprocket will also slow you down more when you roll off the gas. Gearing usually tends to be a compromise. There is no perfect gearing for every corner. As you are discovering
     
  13. electrobiker86

    electrobiker86 Active Member

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    Thanks Jason, with no slipper I have had to learn the braking with the gas on routine particularly in corners 2 4 and 5. Letting off in 4 locked up the tire 3 times causing me to ride off prior to learning to decelerate slower. Gear change would likely effect 7 as well, thanks for the heads up.
     

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