KTM 640 SM Exhaust modification

Discussion in 'Thumpers' started by Sycamore, Apr 21, 2006.

  1. Sycamore

    Sycamore d00b

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    In the interests of science, here's the next layer in the stock European-issue KTM640 SM exhaust.
    With a lot of crude drilling and cutting. I removed that mysterious plate shown on page 1 of this thread.

    This pic is what I got - the next layer.
    This next plate (the one shown here) is about 2 or 3 inches deep into the back of the muffler - probably at the same place that the US exhaust would have the bolts for the Supertrapp discs?
    Maybe this Euro-muffler is simply designed to be not modifiable.

    The sound of the exhaust has changed very little. Up a decibel or 2, a bit less mushy. Performance, dunno yet. Haven't done anything yet to jetting or airbox.
    Maybe I should just leave well enough alone and save my pennies till i can get a Staintune or the like..
    Comments?
    #41
  2. dagwood

    dagwood Banned

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    now if that had six tapped (threaded) holes in it then that is what the us model looks like.
    with a dowl in the hole use a hole saw and cut out the small S pipe. it will come right out...but without the super trapp discs it will be qite abit louder...But WTF do we care how loud it is...it is in the middle of freakin knowhere fer chrisC's sake.:lol3 Hack away.
    #42
  3. Sycamore

    Sycamore d00b

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    It may be the middle of nowhere, but my neighbor is a cop with a 6 mnth old daughter, so too many decibels may not be good for me. Would it work to drill a series of 8 or 10mm holes through that second plate until I'm happy with the flow?
    That way I can graudually adjust. Yes? No?
    #43
  4. meat popsicle

    meat popsicle Ignostic

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    Actually that is one method used by USA Supercrapp owners. I believe it was just a matter of drilling some small-ish holes in that endplate just outside of the center pipe... have to dig around; I didn't find the thread in the index. :doh

    Good idea to do it one at a time and see how it sounds. Plus, you will want to retune the air/fuel mixture each time so you will get good at that process too!
    #44
  5. Sycamore

    Sycamore d00b

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    Yeah I know, I'm busy tracking down all the BST threads looking for advice on mixture setting and my head is spinning. I've only had the bike a few days so I haven't even figured where the mixture screw is.
    And it seems the owner manual doesn't want people touching the carb.
    #45
  6. meat popsicle

    meat popsicle Ignostic

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    You SM has a BST? OK, creeper has his guide HERE. It is indexed under "LC4 Setup Threads".

    Flanny's PDF of his guide is available in my Yahoo briefcase, also indexed under "Other External Links to Downloads". Lots of stuff in there that you might want to 'borrow'.

    Plenty of other useful stuff and fluff in the index. Hopefully I will get the edits done soon and have some cleaning and new additions soon. :D
    #46
  7. Sycamore

    Sycamore d00b

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    Meat, thanks for the links, seems like that's what I need.

    IMO the index is fine as it stands, it's damn useful. That index is quite an incrdible & addictive thing actually.

    The bike's already popping a bit & idling not so good just from removing that first muffler plate so I guess it needs to be a bit richer.

    Problem with the 640 SM is that it has no rev counter, so it's hard to adjust idle mixture screw based on that method of setting a higher idle speed and then adjusting. After listening to a few minutes of idling you kind of forget what the previous idle sounded like...

    How much would you turn your idle mixture to counteract just a bit of leanness from opening the pipes slightly?
    Don't need to answer that if it's going to open a can of worms...

    Thanks anyway for the suggestions so far
    #47
  8. meat popsicle

    meat popsicle Ignostic

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    No tach? Dang...

    The best person to answer your question is more than likely creeper. I have never tried to tune a bike w/out a tach; perhaps there are some others who have that know other diagnostics besides RPMs.

    Read over creeper and Flanny's guides; they might have some info for ya.

    Perhaps you could turn it a hair and then go for a ride and see how that influences the popping? "idling not so good" means what? Idle hunting? The idle dropped lower after the change?

    PS - thanks for the compliment on the index, however I say you're full of dirhams... :lol3
    #48
  9. Sycamore

    Sycamore d00b

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    I suspect the idle always was a bit slow, now it seems to have dropped slightly, stalled twice. Nothing major though, I'll try a light touch on that mixture screw..

    I just came back from a ride (1.30 am, hot as hell outside) and I also noticed that the mid-throttle acceleration now seems a bit dull or flat - that would correspond to something I saw on Flanny's site about running lean on the main jet.
    I tried a bit of choke for a hundred yards or so and the throttle seemed to get more of a kick - does that make sense? Making the mix a bit richer? Or maybe that's oversimplifying it.

    And all of this would (I think) correspond to my heavy-handed opening up of the muffler.

    Which is fine - as long as there's consistency with symptoms. Unpredictability is what I don't like.

    i wish i was.
    #49
  10. lost1

    lost1 Adventurer

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    I bought my Adventure in AUstralia and it had the exact same exhaust as yours. I tried to modify it. Nothing worked other than cutting it open, removing the offending pieces and rewelding it. Basically its not really worth the effort as the thing weighs as much as if it were made out of brick. Order a good aftermarket and wait for it to arrive in the emirates, inshaallah.
    #50
  11. Sycamore

    Sycamore d00b

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    I hate waiting! I will order one when I get enough money, inshallah. I priced Staintune from Oz, I like it but it aint cheap. Maybe in a few months.
    As a temporary fix I cut out the first plate, and then drilled 6 x 10mm holes thru the second back plate, so my brick exhaust sounds much better now, not too loud but good, and much more airflow out the back. The carb was suddenly a lot more lean, so now I'm doing the carb jetting and at the same time putting on a smaller back sprocket.
    I'll see how it goes latter today if the damn wind stops, we've had sandstorm for the past 2 days...
    #51
  12. overlandr

    overlandr Dystopist

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    Heard good reports of the DAM from Germany via Sommer
    #52
  13. meat popsicle

    meat popsicle Ignostic

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    good tip overlandr! go griz got one and he dug it. very quiet, but flowed well. Your orders from Germany might be better than Oz, shipping-wise. And the dam is a slip on; not sure if the Staintune slips on the stock midpipe. :dunno
    #53
  14. overlandr

    overlandr Dystopist

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    They both look similiar stainless steel type oval or round - Jerome the RTW guy said the Dam was the best sound he'd heard ('cept Akra!). I picked up a used Dam in the UK but won't get it for another 6 months or so!!
    #54
  15. lost1

    lost1 Adventurer

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    oh I know sandstorms alright. I rode by myself from Sanaa to Musqat through the desert almost 10 years ago on a Suzuki DR 600. That was one tough ride, following wadis and goat tracks for weeks...

    I was in Dubai last year for a short visit. It was too hot for riding. Imagine. I live in Canada where its too cold, too much snow etc. Trust me I would rather be too hot.

    I hope you have this exhaust thing all fixed up. I drilled mine out too before finally giving up on it.

    lost1
    #55
  16. meat popsicle

    meat popsicle Ignostic

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    What courier service is that?!?
    [​IMG]
    :lol3
    #56
  17. lost1

    lost1 Adventurer

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    Meat, you got the angle all wrong, How in the hell are we supposed to see the DAM exhaust pipe.
    #57
  18. meat popsicle

    meat popsicle Ignostic

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    You are one sick puppy lost1! You're gonna fit right in here... :wink:
    #58
  19. Sycamore

    Sycamore d00b

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    I recognize that baby, if the shot was a better angle you'd see that it's got Acrapovic pipe, not DAM.
    BTW notice the aftermarket Corbin seat, there's a bit of wear but it's still good for a few thousand miles.
    #59
  20. Sycamore

    Sycamore d00b

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    How many air filters did u go through?
    If you were here in summer, you'd remember that it gets up to 50 degrees C (120 F). I'd raher be too cold thanks. The killer in Dubai is that heat combined with massive humidity. 10 minutes on the bike & you are soaked.
    #60