KTM 990 Transmission modification

Discussion in 'Crazy-Awesome almost Dakar racers (950/990cc)' started by BykBoy, Oct 22, 2012.

  1. BykBoy

    BykBoy Meshuganeh

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    Prognosis: The ADV has lot's of power but the current gearing is a compromise. With stock sprockets (16 front - 42 rear), 1st gear is not low enough for off road, and 6th gear does not get great fuel mileage.

    Of course, I know changing the front and rear sprockets can give more low end torque or high end fuel economy. But this impacts all gears, so it doesn't really solve the problem.

    A few years ago, there was a mod kit for the 1100/1150 GS that lowered the 1st gear ratio to provide more low speed torque. Is something like that possible on the 990 transmission? Has anyone considered or heard about modifying the transmission ratios on the 990/950 on the main and counter shafts to make 1st gear is lower and/or 6th gear is higher?

    We have many talented and creative individuals and fabricators here (I'm looking at you CJRacer, Sakurama, BDCW, Touratech, and others...). So come on, there must be a way to do this... :evil
    #1
  2. mousitsas

    mousitsas Long timer

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    SMT gear ratios....
    #2
  3. BykBoy

    BykBoy Meshuganeh

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    Well, it looks like the ADV and SMT have the same ratios. The Super Duke's ratios look to be higher throughout the range and would probably not fit in the ADV.

    .................ADV.......... SMT.........Super Duke

    1st.............12:35........12:35........14:36
    2nd.............15:32........15:32........16:30
    3rd.............18:30........18:30........20:30
    4th.............20:27........20:27........21:27
    5th.............24:27........24:27........23:26
    6th.............27:26........27:26........25:26
    Primary.......35:67........35:67........35:67
    Secondary..16:42........17:41........16:38

    I wonder if the 6th gear sprockets can be swapped so that instead of 27:26, 6th gear would become 26:27. Anyone have a spare gear box laying around? :evil
    #3
  4. mousitsas

    mousitsas Long timer

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    They don't according to this:
    gearingcommander.com
    #4
  5. howl

    howl 990 Adventure

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    #5
  6. BykBoy

    BykBoy Meshuganeh

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    You're right. According to gearningcommander.com, the 2007 950 SM (R) has 26:27. :clap:clap

    Question is: will they fit the 2011 990 ADV?
    #6
  7. geometrician

    geometrician let's keep going...

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    Touratech? You mean the German manufacturer & distributor of (overpriced, questionable) accessories with 135 total posts as a Vendor? Don't think they do much transmission work! :lol3

    Go faster in 6th or drop her into 5th... as for 1st not being low enough offroad, I'm not sure what you're talking about...

    Spend some time looking into the (final drive) gearing threads OC has with lots of info & experience on this issue

    As for the making gears, it's a very complicated & precise set of operations that requires proper machining & grinding of the shaft bore, teeth & gear dogs/mating holes followed by proper hardening & heat-treating. Contact REISHAUER or similar if you're interested but it's gonna cost you big bucks- plus you'd have to supply an entire transmission for mating. Considering they set up assembly lines for GM, Toyota, etc I don't think they're gonna be interested. You could try smaller custom gear manufacturers but most of them are geared (excuse the pun) towards auto transmissions for drag/road-racing applications and are set up w/tooling for a market with 100's of sales a year, not just your two gears. You're looking at the far side of a thousand dollars, easy.

    In the end "poor fuel economy" in top gear vs. the cost of the all the seals & gaskets, donor gearbox/custom gears, etc over the life/miles of the bike isn't cost-effective. :deal
    #7
  8. kamanya

    kamanya Andrew to most

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    I understand what you are trying to do.

    A change to 26:27 would give you less gear than your current Adventure 6th?

    The major reason why I took the Super Duke gearing out was that its 1st is higher and 6th lower than the Adventure gearbox. If I sprocketed for low speed stuff, the higher speed cruise was compromised and visa versa.

    Your Adventure gearing is currently the widest spread of gearing on any of the LC8 engines. In other words you'll not get a lower low or a higher highest gear in any other model LC8 Engine unless you get custom made gears made$$$$.

    You seem to be looking to gearing to solve a consumption issue. Sadly these engines are not known for their efficiency so do what I did....

    Get bigger tanks!

    [​IMG]
    #8
  9. BykBoy

    BykBoy Meshuganeh

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    You are correct. Going with a 26:27 would give me a .962 ratio, while the current 27:26 setup has a 1.038 ratio. Not sure what I was thinking... :huh

    To get the desired improvement, I would need a 28:25 and it would cost $$$$!

    I've been thinking about these... I would love to get a set, but they are so expensive! On the flip side, they do provide lot's of surface area for stickers...:D
    #9
  10. tahoeacr

    tahoeacr Long timer

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    #10
  11. snowhawk jockey

    snowhawk jockey Slack Jaw Gaper

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    #11
  12. Pantah

    Pantah PJ Fan from Boston

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    I hope you sell it dirt cheap when you are done screwing it up.
    #12
  13. tahoeacr

    tahoeacr Long timer

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    Still stock injectors. Don't have em maxed out yet. Heck, their probably at less pulse wideth than an Akra map:rofl.
    #13
  14. sakurama

    sakurama on an endless build

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    While I appreciate the faith gear cutting is some serious stuff and way over my head. Expensive too. As was mentioned your best bet is to see about swapping ratios around but the mileage thing - that's trying to put lipstick on a pig. This bike can pass anything on the road but a gas station. :cry

    Gregor
    #14
  15. grinns

    grinns Semper Fi

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    #15
  16. Jonny955

    Jonny955 Been here awhile

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    I LOVE this statement. I think I'll use it when people ask me about my bike :lol3

    Thanks!

    Jon
    #16