What sprocket sizes are stock on 990R

Discussion in 'Crazy-Awesome almost Dakar racers (950/990cc)' started by alongat, Jun 30, 2013.

  1. alongat

    alongat Long timer

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    So I can tell by the part number that my bike came with a 16tooth front sprocket but when I look at the rear, I can't tell though I think I can almost see a "42" or"43" stamped on it. I've recently gone with the 19/17 wheel setup on my 2012 990 adventure R and obviously the geari g ratio has changed. Wile I appreciate the new found acceleration and wheeliness, I don't want to be spinning that high on highway crushing / longer runs and I was happy with the original gear ratio. To get it back to stock, I need to either reduce the rear sprocket tooth count by three or add one tooth up front but when I look at the front area, I'm not convinced that there is actually enough room for a 17 tooth sprocket given the chain,s current proximity to the slave cylinder, etc. can anyone confirm if there is in fact room to run a 17 tooth up front? It seems like the better choice compared to reducing the rear by three teeth. Bigger sprocket up front is easier on the chain and reduces drivetrain losses, right?

    Thanks in advance
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  2. alongat

    alongat Long timer

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    And I just counted the teeth on the back sprocket - 42 so my bike has a 16/42 setup.
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  3. laramie LC4

    laramie LC4 crash test dummy!

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    yup 16/42 is the stock ratio on the 990R. divide 42/16 = 2.625, 45/17 = 2.647, 45/15 = 3.0 and so on....the lower the number, the taller your gearing.

    i have no idea how your smaller tires will affect/change the ratio but i'm sure a little google work will get you a formula.

    laters,

    laramie :beer
    #3
  4. alongat

    alongat Long timer

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    I've done the calculations - based on my new wheel/tire circumference, going with one tooth up in the front or three teeth down in the rear will get me extremely close to what I had before changing the wheels. I'm wondering if people are running 17 tooth front sprockets from a clearance standpoint.
    #4
  5. rider911

    rider911 Shortcut Navigator

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    All 990s used to come std with a 17T front sprocket. Im not sure what year they started putting 16T on.
    I use 17/45 on my bike most of the time but if im doing a softer ride with some bemmers then I will use 17/42 to give it a few more legs.
    #5
  6. alongat

    alongat Long timer

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    Ok, so it sounds like a 17 does fit. Now, does anyone have an opinion on whether or not to get a standard front sprocket or the KTM dampened sprocket like the one on it now? Can anyone actually feel any difference?
    #6
  7. spafxer

    spafxer Long timer

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    The 17 dampened sprocket fits for me, and I do not notice any noise difference from the un dampened sprocket.

    I assume when they do noise tests with machines, the dampening must make a difference ! (of course they use stock mufflers too. Long gone for most of us!)
    #7
  8. Trail bandit

    Trail bandit Random adventurer

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    I like the legs on the 17/42. Note. It doesn't look like its going to fit. You've got to get it sitting just right then it just slips in place with no room to spare.

    Rekluse clutch gives the best of both worlds. You can run good highway gearing and crawl speeds with no clutch use.

    I'm up to 160 miles on a tank of gas. 1/3rd dirt trails and balance highway. Very interested when I go to fill up what the mpg is going to be. Low fuel just came on.
    #8
  9. woodchuckexc

    woodchuckexc Been here awhile

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    Why an "R" if you plan on riding street? It seems like such a waste to take a thorough bred offload beast and mount street wheels.
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  10. FakeName

    FakeName Wile E Coyote SuperGenius

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    It's always been my understanding (I could be wrong, and often am) the dampened sprocket is meant to be gentler to the power train.
    #10
  11. spafxer

    spafxer Long timer

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    There, you are not wrong ! :freaky



    :lol3
    #11
  12. MortimerSickle

    MortimerSickle Semi-Adventurer

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    spafxer has it right: Rear cush yes, but the rubber on the front sprocket dampens only noise. It does nothing to cushion the drive.
    #12
  13. keener

    keener Speed changes you.

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    And it dampens a lot of noise, the front sprocket that is... I tested this riding with engine off in natural. I compared two sprockets.
    #13
  14. keener

    keener Speed changes you.

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    #14
  15. MortimerSickle

    MortimerSickle Semi-Adventurer

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    I guess I'm deafer than I had thought. :D
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  16. Two Moto Kiwis

    Two Moto Kiwis Homeless Somewhere

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    Using 16 T instead of 17 T makes the LC8 a lot smoother at the bottom/mid range, not so much difference at highway speeds.

    We are going to stick with 16 front and put the smaller rear on to keep the smoothness.

    As far as chain life, I used to run 14T on the Ducatis (factory 15) and chain life was pretty much identical to my (later) 990 SMR at 17 T
    #16