Supercharged KTM LC8 motard build

Discussion in 'Some Assembly Required' started by OldDog, Nov 23, 2013.

  1. OldDog

    OldDog aka Hugh Jarse

    Joined:
    Feb 20, 2005
    Oddometer:
    4,835
    Location:
    Mudgee, Australia
    ....so where to begin?
    I've been building bikes for a long time. I think one of my first really serious ones was a supercharged Norton 500cc dominator using a vane type blower which was only good for around 5000 (blower) rpm, using a draw through SU carby. It worked quite well and certainly surprised a mate of mine on his CB750/4!
    I sold that and moved up in the world to a ZX12, which eventually was fitted with a big block kit and nitrous, in the end it pulled over (measured) 200 mph and was still quite streetable. I learnt a lot about how to tune a fuel injected bike from that thing, there are stories of me riding around town with a laptop strapped to the tank making fuel and igniton adjustments.
    After that I restored a few bikes then went on to build a Ducati 900 Monster dirt bike http://www.advrider.com/forums/showthread.php?t=428685 that thing taught me a lot about suspension and I'm pleased to say it handled both dirt and tar very well. Its sitting in the back of the shed waiting for its turn to be reborn, using some of the cast off parts from this build.

    Several bikes later and I ended up with this
    [​IMG]
    and fell in love with just how much fun it is to ride.

    The plan was hatched to build another special, this time around the mighty LC8 KTM with a view to making it very streetable, not one of these beasts that you can barely fit or be comfortable on. So I bought this 950S which I've started wrecking out as I don't need some bits
    [​IMG]
    The plan turned into a supercharged "super motard" esque machine using the standard carbs in a blow through design. This idea got me reading Tommy J's thread on turbo'ing (you almost had me sold Tommy:D) http://www.advrider.com/forums/showthread.php?t=656921 where I got to realising...it's probably gonna be a lot easier using fuel injection!
    So cruising ebay the other day I happened upon this little beauty, a 2006 KTM superduke
    [​IMG].
    At this point I'm stripping them both down and trying to work out which frame, swingarm etc to use. No doubt that I'll be using the 950S forks though.

    At this point I've found that the 950S frame is longer than the superduke's and in some places narrower. The Superduke has a shorter swingarm than the 950S. On the plus side theres a hell of a lot of stuff that changes over too! I found the duke a bit short but handles so well I'm dumbfounded. I'm thinking of either fitting the longer swingarm to the duke to add a little stability (along with the 950 forks which have a leading axle as well as the extra length. Or fit the shorter swingarm to the 950 similar to the KTM super motard does, although the SM's front axle mounts at the base of the fork rather than leading.

    Questions I have that people may be able to help with, can I lengthen the standard duke shock ie is there an internal spacer like in the 950 shock?

    Any suggestion, observations or commenst are more than welcome!

    Cheers

    Bill
    #1
  2. freetors

    freetors Been here awhile

    Joined:
    Feb 20, 2011
    Oddometer:
    979
    Location:
    Collinsville, OK
    As a lover of forced induction I look forward to reading this!
    #2
  3. mousitsas

    mousitsas Long timer

    Joined:
    Oct 10, 2008
    Oddometer:
    3,006
    Location:
    Athens, Greece
    We will have a great time following this thread, thanks OldDog!

    Regarding forks, I would say that the choice should be based on wheel size. Leading axle will not work well with a 17" rim, since the trail will be very small indeed.
    I cannot answer your question on the SD shock, but I know that the SDR has a longer shock than the SD with tighter valving and stronger spring, but possibly not very easy to find.
    #3
  4. Speedzter

    Speedzter Been here awhile

    Joined:
    Jan 5, 2004
    Oddometer:
    685
    Location:
    Vic' Australia
    I will be watching with interest !!
    #4
  5. srad600

    srad600 Been here awhile

    Joined:
    Sep 30, 2009
    Oddometer:
    689
    Location:
    Oakland, Kalli Fornia
    I'm afraid I cannot help with your suspension questions, but there are a few guru's around the OC that may be able to assist. I will be watching this thread though, a supercharged 950/990 sounds like fun. :beer
    #5
  6. sailah

    sailah Lampin' it

    Joined:
    Aug 12, 2005
    Oddometer:
    5,823
    Location:
    Turning expensive metal into scrap
    That's one helluva start(s) to a bike build!!

    Looking forward to it:D
    #6
  7. gavo

    gavo Slacker

    Joined:
    Jan 5, 2010
    Oddometer:
    1,896
    Location:
    Gympie QLD
    :lurk
    #7
  8. OldDog

    OldDog aka Hugh Jarse

    Joined:
    Feb 20, 2005
    Oddometer:
    4,835
    Location:
    Mudgee, Australia
    Thanks for that Mousitsas. I've fitted the shorter SD swingarm and 17 wheel up to the 950S frame and fitted the 17 wheel from the SD to the 950 using the standard S forks. The forks are worn and have sagging springs but I ended up with a rake of 26 degrees and a trail of approx 70mm:eek1. Yeah that ain't gonna work!

    I fitted the longer swingarm and 17 wheel to the SD and it looks like a drag bike :lol3 but still this may end up being the best option, with the 100mm longer wheel base the bike will be a bit more stable and would not have as much of a tendancy to loft the front wheel with the extra grunt.

    Once I have the base bike organised and running, then we'll move onto the blower.
    #8
  9. mousitsas

    mousitsas Long timer

    Joined:
    Oct 10, 2008
    Oddometer:
    3,006
    Location:
    Athens, Greece
    That I think is the best approach too, but you will need a stiffer shock spring due to the longer arm.

    :clap
    #9
  10. OldDog

    OldDog aka Hugh Jarse

    Joined:
    Feb 20, 2005
    Oddometer:
    4,835
    Location:
    Mudgee, Australia
    Mmm thats a good point, due to the extra leverage.
    #10
  11. snowhawk jockey

    snowhawk jockey Slack Jaw Gaper

    Joined:
    Jul 5, 2005
    Oddometer:
    1,134
    Location:
    The other Center of the Universe: Bend, Oregon
    TommyJ had quite the thread on cloaked induction! I like that you are pulling in all the models of LC8 and shaking out the right blend of chassis for your HP bike. Inmate Head2Wind is compiling a similar concept, less the plenum and fan. He has been swapping arms and legs on an Adv in his OC thread, to find the slicingest Adv with 17" wheels.

    Dunno if the SD shock has a spacer, but the SD forks should have spacers. I always wanted to run the longer Adv arm on the back of my SM, it would soften a too stiff shock and give space for a taller tire. Not that any one wants to run a sand paddle, except me, but it sure would be fun in the sand drags...
    #11
  12. Roadracer_Al

    Roadracer_Al louder, louder, louder!

    Joined:
    Aug 5, 2007
    Oddometer:
    1,726
    Location:
    Oakland, CA
    Here is my suggestion about your various suspension options.

    Longer swingarm: yes. Once you get the puffer working, you'll want the extra wheelbase.

    Forks, etc. -- accurately measure all the bits, and (lo-tech) make cardboard cutouts and measure rake & trail directly, or (hi-tech) make a drawing in your favorite drawing program or CAD if you have it and move all the suspension bits that way and measure.

    When you go from 21" to 17" rims, you lose both rake and trail. Consider that when choosing your triple clamps and forks.
    #12
  13. OldDog

    OldDog aka Hugh Jarse

    Joined:
    Feb 20, 2005
    Oddometer:
    4,835
    Location:
    Mudgee, Australia
    Well its been a very busy few days in the shed. I have both bikes stripped right down now and after a lot of measuring ( thanks for the advice Al) I have decided to go with the SD suspension dimensions etc rather than the 950S. Big problem is the SD frame is a stat write off so it can't be reregistered and fair enough too as it has a dent in the left hand side of the frame just at the steering head. Sooooo, tomorrow we're cutting up the 950 frame and we're going to shorten it up. It won't be quite as short as the SD frame, I want a little extra knee room as I'm pretty long in the leg. We'll also retro fit the reset hangers and other brackets at the same time. Biggest bummer on this will be that I'll lose the centre stand.

    Saturday afternoon I should be right to start painting the fram etc and then start the reassemble. I'm going to move the oil tank out of the way I think to make room for the blower. Possibly down to the fron of the frame where the battery is mounted at the moment.
    I'm going to use the 950 swing arm, and will use the SD forks for now just to get it into a rolling test bed stage. Future plans will be either SM forks or lengthen the SD ones if thats possible. Going from what Snowhawk says it does look like theres a spacer in there (on the parts list)
    Will post up some pics when I get started on the paint.

    Cheers

    Bill
    #13
  14. Phrog

    Phrog Terra Australis

    Joined:
    May 24, 2009
    Oddometer:
    405
    Location:
    34.0544°S, 150.6958°E, AUSTRALIA.
  15. OldDog

    OldDog aka Hugh Jarse

    Joined:
    Feb 20, 2005
    Oddometer:
    4,835
    Location:
    Mudgee, Australia
    Actually yeah been keeping an eye on that thread. 2WD! Bloody impressive stuff, I suspct it's a bit beyond my ability but yer right, imagine that with a blower:wink:

    Well we've done some cutting and we've done some welding. We've shortened the 950S frame down by 50mm taken from between the steering stem and the first frame upright. We resisted the temptation to change the steering angle and have left that stock. As it stands the rake should be around 25 degrees and 104mm of trail using the standard SD forks. If I extend the forks to 200mm of travel (and change the rear travel as well) then we should see the rake stay the same and an increase of over 5mm of trail. So still a fast turning bike, but not as diabolical as the standard SD:lol3....and a lot faster than the standard 950S as well.

    Well thats the plan anyway, guess we'll know when I bolt the bike back together...

    Cheers

    Bill
    #15
  16. OldDog

    OldDog aka Hugh Jarse

    Joined:
    Feb 20, 2005
    Oddometer:
    4,835
    Location:
    Mudgee, Australia
    Bit of progress over the weekend. Frame is painted and I've got the bike rolling again. Since this pic i've fitted the radiator, brakes etc back up. I'm in a bit of a rush to get the main bits back on as i start a new job on Wednesday which will have me living away from home during the week, don't want any important bits to go missing or (more likely) me forgetting where bits go.

    [​IMG]

    Looks pretty sexy in white, but it gets dirty real easy.
    #16
  17. willh

    willh Adventurer

    Joined:
    Feb 23, 2005
    Oddometer:
    42
    Location:
    Shefford, Quebec
    :lurk

    What's the tank seat arrangement going to be?
    #17
  18. OldDog

    OldDog aka Hugh Jarse

    Joined:
    Feb 20, 2005
    Oddometer:
    4,835
    Location:
    Mudgee, Australia
    At this stage Will I'm gonna go with the standard tank and seat as I want to get the bike streetable, then do the blower which will dictate how the body work will end up. Ideally my plan is to make a tank out of thin alloy sheet laminated and blind rivetted together. Think of the skin on a fighter plan with its exposed rivet heads and you'll get the rough idea. Not easy but should be a good conversation starter:rofl
    #18
  19. OldDog

    OldDog aka Hugh Jarse

    Joined:
    Feb 20, 2005
    Oddometer:
    4,835
    Location:
    Mudgee, Australia
    Well I have it basically back together and running, considering of mnodified the wiring to get the electrics, battery etc to under the seat, I'm pretty happy with that result:D
    The empty space where the battery used to go down at the lower front will be the position for a new fabricated oil tank. Once that is done I'll take off the old oil tank and that's where I'll mount the blower.


    [​IMG]

    Things are going to slow down for a bit as I've taken up a new job which has me out of town all week, so I will be mainly working on it during weekends.
    Oh and with the 950S swingarm fitted I'm coming up with a rake of 21 degree and a trail of 103mm. Seems a bit out to me so will remeasure again next weekend.

    Cheers

    OD
    #19
  20. Te Hopo

    Te Hopo AKA Deanohit

    Joined:
    Sep 25, 2007
    Oddometer:
    1,761
    Location:
    Either Picton or Kokatahi, New Zealand
    I've always liked the Super Dukes and swore I would own one one day after taking a spin on a SD R.

    This is a great sounding project, it looks real promising stripped down with that longer swingarm. :clap
    #20