2012 KTM SX250 with 380 engine
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Thread: 2012 KTM SX250 with 380 engine

  1. #1
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    Default 2012 KTM SX250 with 380 engine

    Hi there

    Been racing supermoto on 4 strokes for 7 years now, so it was time to try something different, so this summer i bought an SX380 from 2000 and
    made it ready for some supermoto.... ..and what a powerfull engine, most fun i had in a long time ....only the chassis let me down some, it
    was quite soft and made the bike flex a lot.

    Pic of my SX 380




    One way to fix the flexing chassis is to put the old 380 engine in a new bike, simple.. maybe not simple but definitely possible as others
    have already proved including a certain mr. J. Jasinski who just happed to win the 2012 German supermoto championchip for the big bikes, on
    a Husaberg with this concept.

    So i bought this one, a used 2012 SX 250 in good condition.



    First step was to rebuild the 380 to MX for storage and take out the engine






    Then it was time for the SX250...









    ...... and that was the easy part, let the games begin....

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  3. #2
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    This is going to be good. I love it.

  4. #3
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    suuuuubbbbbddd

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  6. #4
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    interesting idea. make sure and pull this shit off proper

  7. #5
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    Quote Originally Posted by The Wolf View Post
    interesting idea. make sure and pull this shit off proper
    agreed... dont let the honda boys show you up now!

  8. #6
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    I also wish to bear witness to this badassery

  9. #7
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    OMG another 380.
    I have to sell mine 380 and buy something else. Because soon everyone will be such ride
    KTM 380 SMR
    DR-Z400SM 3x3 , FCR39MX , JD , MRD/SSW , MAGURA/BREMBO4P/BRAKING320MM, IMS 2.6 SOLD

  10. #8
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    Time to mount the engine, it would be easy just to relocate the original brackets but i want the possibility to re-mount the original 250 engine in the unthinkable case that i schould have a failure on the 380.
    So instead im going to weld some treaded bushes in the frame, 2 on each side for the middle brackets and 3 on each side for the front brackets, there is the biggest difference between the 250 and 380 so the 2 lower holes are for the 250 and the 2 upper holes are for the 380.

    first i made a tool for marking where the bushes schould be



    Then i drilled the holes for the busches.



    With this small tool i got the bushes alligned so i could secure them with a spot of tig-welding.



    The welding process is a little more complicated, first it is important to heat the frame around the welding area to min 100 degrees celcius.





    With some special fillerwire (thermanit x) i then tig-welded the bushes and quickly insulated the area so it diddent cool too fast.



    This little job takes longer than you can imagine, next up is brackets.

  11. #9
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    Why so intensive welding the bushings? is it steel, cro-moly? reason for the preheat? whats the bushing material?

    z
    fund the turbo XRR project
    http://www.supermotojunkie.com/showt...on....-for-now XRR-T Build Thread
    FS: http://www.supermotojunkie.com/showt...ipped-lower-48 A*'s leather jacket!!

  12. #10
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    Quote Originally Posted by proz07 View Post
    Why so intensive welding the bushings? is it steel, cro-moly? reason for the preheat? whats the bushing material?

    z
    Bushings are common construction steel, frame is crome-moly, the reason for preheating is to prevent cold steel from absorbing the heat from the welding and thereby weakening the welding. This is very likely overkill, but i want to be certain that i did the bedst i could do
    Last edited by andyracing; 11-23-2012 at 11:32 AM.

  13. #11
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    Quote Originally Posted by andyracing View Post
    Bushings are common construction steel, frame is crome-moly, the reason for preheating is to prevent cold steel from absorbing the heat from the welding and thereby weakening the welding. This is very likely overkill, but i want to be certain that i did the bedst i could do
    Thats what i thought, the preheating is probably a good idea to minimize heat input during the welding and prevent cracking of the cro-mo.

    nice work
    z
    fund the turbo XRR project
    http://www.supermotojunkie.com/showt...on....-for-now XRR-T Build Thread
    FS: http://www.supermotojunkie.com/showt...ipped-lower-48 A*'s leather jacket!!

  14. #12
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    Andyracing are you by any chance from Denmark, because it sure does look like slots pilsners in the pictures?

  15. #13
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    Yup, subscribed!
    Quote Originally Posted by crash279 View Post
    When you try to get clearance for the sprocket on the front forks and the axle won't fit is when you know that you've had a few too many lol.

  16. #14
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    Quote Originally Posted by Langeland View Post
    Andyracing are you by any chance from Denmark, because it sure does look like slots pilsners in the pictures?
    Check the graphics on the 250, im pretty sure he is.

  17. #15
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    I like how i noticed the beers but the it didnt even cross my mind to check the graphics

  18. #16
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    Yes im from denmark... and i like beer

  19. #17
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    Subscribed! Great project with good ideas
    2008 Husqvarna SM450R
    Check out the Supermoto Central Shop for the new Supermoto Central gear!

  20. #18
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    very nice! Like the welds. Keep it up!

  21. #19
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    Quote Originally Posted by szymon View Post
    OMG another 380.
    I have to sell mine 380 and buy something else. Because soon everyone will be such ride
    No soon 380's will rule the world

  22. #20
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    finished the brackets for both engines, just need to engrave info of position and what engine the specific bracket is for, then it is off to a coat of metalizing.


    Cleaned up the frame ready for stripping of the orange powdercoating so it can be re-painted in the original black.


    What a b!tch to disasemble the Y-pipe in the frame. First forced the rubber of the Y-pipe (no damage) with a big flat screwdriver, then i heated the Y-pipe with my torch to break the glue on the tread, then i could unscrew the long pipe with a costum made tool...


    Made a quick engine stand.


    Painted it black and mounted the engine.



    Engine ready for a proper overhaul....

  23. #21
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    andy, the quantity of your fans will riiiiiise - worldwide! I remember people in australia talking about JJs achievments

    keep us updated with the development of this bike

    have fun
    pat

    2 strokes - the future

  24. #22
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    Updates please!! ?

  25. #23
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    took the engine apart to make a list of parts that was needed to have a race-ready engine, i wanted an EXC gearbox for a bigger gap between gears, i also wanted to replace connection rod, piston an main bearings.


    At first glance, everything looked in very good condition, im in doubt if i need to replace connection rod and piston..... ill by the parts anyway, then i can always decide later when im going to replace them.

    clutch basket has the usual wear, im probably going to mill a few tenth of a mm off the surface.


    Engine covers must be prepped for paint, i think the original color is ugly, so at the moment im thinking a dark gray or similar may look good.


    Paint stripper at work.....



    Frame is put on hold at the moment, i have to investigate a little on stiffening the frame as seen on the pic below.

  26. #24
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    Congratulations on choosing the correct engine configuration!

    Sure looks like 380's are the way of the future, gaining lots of popularity just recently.

    Very nice work so far!

  27. #25
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    Top bracket was too much work to do at home, so i had 3 parts lasercut at work, 2 sides and one middle support in the middle, will look good when metalized. Original 250 to the right.







    Rear damper off to Germany for rebuild for supermoto, spring is ok, but shims must be replaced.

  28. #26
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    Bought christmasbeer, build can continiue.....


    Back to the frame, i took it with me to work and put it on the table of one of the big millingmachines we have in the factory. Then i bolted the rear of the frame to the table and put a steelbar through the headtube so i could pull it sideways and get an idea of where the frame would flex and by how much using measuringclocks in more directions.


    Had some trouble finding crome-moly steel for the reinforcements, but after a good search i found a couple of BMX handlebars i could cut up.


    maybe something like this


    Checked the engine carefully, only 2 bearings need replacements, so i ordered the bearings and a bunch "just in case" parts. While waiting for the parts i drilled the cases from the original 15mm hole to 17mm to fit the 250 bolt. Not to risk anything, i put a weight on the handle and turned the drill by hand, it took some time but the result vas good.


    EXC gearbox has arrived

  29. #27
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    awesome build i love the machine work that you are doing!

  30. #28
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    great project indeed.

    the only thing I'm not getting is how the 2 added sections on the bottom of the frame would increase strength. they don't look attached to eachother in the middle unless I'm seeing it wrong.

    seems like simular mods were done to the frame when jasinski was still on a 650 berg, but this setup makes sense as far the strengthening the frame goes because here you have actual crossbars attached to the other frame rails.


  31. #29
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    Great to see so much top drawer fabrication work going into it. I'll be keeping a close eye on this one.

  32. #30
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    I cannot imagine that the 2 sections are not welded together, if they are not, then, as you say, they will have no effect. I assume that they are welded and serve the same purpose as the X on the 650, only with rounded ends.. (?)

    Im also thinking of making something on the front of the frame just under where the exhaust is coming out of the frame, this is where i could measure the most flex, but not much room...

  33. #31
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    nice andy!!!
    i will see it in germany!
    it is a lot of work to get it stiff an swingable...

  34. #32
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    got my new carburettor with TPS sensor, i need this for a programmable ignition.




    The EXC gearbox i got was not 100% interchangeable with the SX gearbox, i had to use the SX primary shaft and change 3, 4 and 5 gear wheels, the seconday shaft was a direct swap.




    Checked chrankshaft, it was straight within 0.03mm



    Not much to right now, im waiting for parts from paint, glassblasting, metalizing and a bunch of spareparts....

  35. #33
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    I see a RD350. Here is mine

    Otherwise awesome work.
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  36. #34
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    Spareparts arrived, now i can start reassembly of the engine.



  37. #35
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    Dude... the Jochen Jasinski videos are indeed an inspiration! 2T all day! I like this build!!!
    Meeners | KTM 950 SuperMoto | KTM 625 SMC | Genuine Blur 150

  38. #36
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    Hi Andy,

    i also want to change my sx gearbox into a exc gearbox.
    Which boxes will fit in this engine?

    Thanks

    ok I see you have the older gearshaft without hydraulic clutch.
    Last edited by gigi03; 12-19-2012 at 08:52 AM.

  39. #37
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    What (programmable) CDI do you want to use?
    KTM 380 SMR
    DR-Z400SM 3x3 , FCR39MX , JD , MRD/SSW , MAGURA/BREMBO4P/BRAKING320MM, IMS 2.6 SOLD

  40. #38
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    i also want to change my sx gearbox into a exc gearbox.
    Which boxes will fit in this engine?
    I got my gearbox from a EXC 250 from 1994, primary shaft is different due to different clutch but all the gears are the same as the EXC 380, so you simply just strip your SX380 primary shaft and put on the gears from the EXC 250 shaft. I cross checked parts numbers on a lot of KTM gearboxes, and often the same gears are used in different bikes.



    What (programmable) CDI do you want to use? .
    If everything works out, it schould be one from these guys.... http://www.ignitech.cz/english/aindex.htm
    They mainly make iginitions for roadracing and streetbikes, but they told me they had something for me too.... still work in progress.

  41. #39
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    Regarding the frame stiffening, this is the model I'm using to make my modifications. It's an HMC frame from an RFS bike, but you might be able to draw some inspiration from it. The three notable modifications I have been able to identify are:

    -Plating behind the peg brackets, where the stamped steel is typically hollow
    -Lateral brace at upper engine mount
    -Vertical brace at steering stem

    I'm not a chassis engineer but I think you will reach a point where too much rigidity will have a negative effect, so don't go overboard with the stiffening. Hope this helps.

    #720 KTM 450SMR
    www.FLsupermoto.com

  42. #40
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    here is a better view of the bracing on this 380's frame


  43. #41
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    I diddn´t stiffering the 250 frame more. And I think it works.
    The main difference is to modifi the fork and damper.
    The Setup is much different to the 4stroke.





    Attached Images Attached Images
    Last edited by gigi03; 12-19-2012 at 11:02 PM.

  44. #42
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    Is that an RD350 in the other picture?

    I fixed my picture not loading, awesome work by the way.

    http://www.myspace.com/aurorasnowband

    05 Husaberg FS650E
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    Trackday Counter: 8 / Crash Counter: 2

  45. #43
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    "I'm not a chassis engineer but I think you will reach a point where too much rigidity will have a negative effect, so don't go overboard with the stiffening."

    "The Setup is much different to the 4stroke."

    +1

    Too stiff is easily achievable.
    There is definitely room for improvement (especially with supermoto) in the rigidity of those frames, but make it too stiff/rigid and the bike will start to loose feel at high cornering speeds (higher g-forces).

    The lower cradle is a great place to start. I would also be looking at other motor mounting areas, suspension mounting areas, and any area/section of the frame where the flex that is required may be influenced by outside forces/mass (like the motor, suspension, pegs, etc.)
    1993 Honda VFR750F
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  46. #44
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    Quote Originally Posted by hey Johnny Park View Post
    Is that an RD350 in the other picture?

    I fixed my picture not loading, awesome work by the way.



    Nope, but close, its a DS7 from 72, its been changing owners since 82 but none of them ever got it on the road, so thats ny next streetbike project.
    I made a streetbike before:


    Video made by Webmaster of supermotard.dk

  47. #45
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    After spending christmas skiing in Austria, its back to building my bike. Just before i left for christmas, i got my frame and enginecovers back from powdercoating aswell as the cylinder and cylinderhead from glassblasting and the enginebrackets from metallizing.

    Frame:


    Cylinder and brackets:




    I put the engine together without any major problems, changed 2 gearbox bearings, all seals and gaskets. One problem got my attention, the valve in the exhaust port was not ajusted properbly and the pistonrings was rubbing on the valve ...took it all apart and cleaned it, fortunately no damage and i put everything back together and ajusted correctly.

    Shiny spot on the right side of the valve shows where the pistonring was rubbing.



    Final engine assembly.



    Engine mounted in frame.

  48. #46
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    Quote Originally Posted by andyracing View Post
    After spending christmas skiing in Austria, its back to building my bike. Just before i left for christmas, i got my frame and enginecovers back from powdercoating aswell as the cylinder and cylinderhead from glassblasting and the enginebrackets from metallizing.

    Frame:


    Cylinder and brackets:




    I put the engine together without any major problems, changed 2 gearbox bearings, all seals and gaskets. One problem got my attention, the valve in the exhaust port was not ajusted properbly and the pistonrings was rubbing on the valve ...took it all apart and cleaned it, fortunately no damage and i put everything back together and ajusted correctly.

    Shiny spot on the right side of the valve shows where the pistonring was rubbing.



    Final engine assembly.



    Engine mounted in frame.


  49. #47
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    Shortend torquechamber, this was necessary to make room for the engine.




    Plastic on the subframe had allmost cut through one of the framerails, i welded this as well.




    Next job is a little more complicated, the 2 coolant hoses must be conected to the cooler, i can relocate the studs, but then i have a one-of cooler. At the moment im thinking of blocking the lovest stud and then cornnecting the hoses with the cooler through a DIY Y-piece.

  50. #48
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    Coming together real nice, I love the job you are doing.
    XS650 Good work too! I'm pretty sure I've seen that bike around the web somewhere...
    Quote Originally Posted by crash279 View Post
    When you try to get clearance for the sprocket on the front forks and the axle won't fit is when you know that you've had a few too many lol.

  51. #49
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    Oooooh can I buy your step up seat?

    I love this build! So much attention to detail! What class and what conference do you race in Germany?
    Last edited by Meeners; 12-29-2012 at 01:17 PM.
    Meeners | KTM 950 SuperMoto | KTM 625 SMC | Genuine Blur 150

  52. #50
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    Loving the project! Will be great to see this when its done, frame looks very nice

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