KTM RFS/SXF Hybrid

Discussion in 'Thumpers' started by jar944, Feb 23, 2011.

  1. jar944

    jar944 Been here awhile

    Joined:
    Aug 2, 2010
    Oddometer:
    751
    Location:
    Chantilly VA
    Ok so this isnt the first hybrid KTM RFS motor in a 250-450/505 SXF frame(seel links below) and likely will not be the last, but I felt like posting it anyway.

    my 2nd hybrid *may* be the first to use a 250sxf frame

    other hybrid build threads
    http://www.ktmtalk.com/showthread.php?t=375749
    http://www.advrider.com/forums/showthread.php?t=620478
    http://www.ktmtalk.com/showthread.php?t=408919
    http://www.dirttricks.com/rfs_in_new_frame.htm
    ride test
    http://www.enduro360.com/2010/09/27/featured/the-dirt-tricks-ktm-rfs-hybrid/

    This was the first thing I noticed, once I cut the lower engine mounts of the frame (to sit the engine inside.) There was much less plumming clearance than I expected. <!--?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:eek:ffice:eek:ffice" /--><o:p></o:p>
    [​IMG]<o:p></o:p>
    <o:p></o:p>
    dirt tricks got around this by machining a 90 degree adaptor for the t connector (as can be seen below)<o:p></o:p>
    <o:p></o:p>
    [​IMG]<o:p></o:p>
    <o:p></o:p>
    The main issue with using the full height RFS motors (450 exc/mxc, 520/525) is the exhaust clearance around the yoke area. I chose to cut and weld in sections of a sacrificial 250sxf engine cradle.<o:p></o:p>
    [​IMG]<o:p></o:p>
    [​IMG]<o:p></o:p>
    <o:p></o:p>
    [​IMG]<o:p></o:p>
    [​IMG]<o:p></o:p>
    <o:p></o:p>
    [​IMG]<o:p></o:p>
    <o:p></o:p>

    Yoke finished, lower mounts in:<o:p></o:p>
    <o:p></o:p>
    [​IMG]<o:p></o:p>
    [​IMG]<o:p></o:p>
    [​IMG]<o:p></o:p>
    <o:p></o:p>

    More to come.<o:p></o:p>
    #1
  2. BRYANDENNY71

    BRYANDENNY71 Been here awhile

    Joined:
    Sep 24, 2010
    Oddometer:
    118
    Location:
    Garden Grove, CA, USA
    Why?
    #2
  3. jar944

    jar944 Been here awhile

    Joined:
    Aug 2, 2010
    Oddometer:
    751
    Location:
    Chantilly VA
    1. RFS bikes handle like a truck. (Terrible)
    2. SXF bikes handle very very well
    3. Not even a worked 505 can match the HP and Tq of a 600-613cc rfs
    4. SXF (RF4) motors dont live long
    5. RFS motors do live long.
    #3
  4. LukasM

    LukasM Long timer

    Joined:
    Nov 15, 2006
    Oddometer:
    5,429
    Location:
    On a RTW ride - currently SE Asia on the way to OZ
    :thumb

    Watching this one closely.

    Did you fix the frame somehow for welding or were you not concerned with distortion?
    #4
  5. jar944

    jar944 Been here awhile

    Joined:
    Aug 2, 2010
    Oddometer:
    751
    Location:
    Chantilly VA
    I kept the engine bolted in as much as possible during the welding/fitment.
    #5
  6. dentvet

    dentvet Long timer

    Joined:
    Aug 4, 2008
    Oddometer:
    1,375
    Location:
    hunt country virginia
    lookin pretty good. Have you figured out what makes the new chassis better? I'd like to see the frames side by side.
    #6
  7. jar944

    jar944 Been here awhile

    Joined:
    Aug 2, 2010
    Oddometer:
    751
    Location:
    Chantilly VA
    Rigidity.

    Each generation of RFS frame got stiffer. The rear suspension geometry changed as well.

    250sxf 450sxf 560smr
    [​IMG]
    [​IMG]
    #7
  8. LoCoMatt

    LoCoMatt Busy

    Joined:
    Jul 14, 2009
    Oddometer:
    491
    Location:
    Good 'ole Loudoun County, VA
    If you have the skill and desire, why not?

    Looks cool, good luck!
    #8
  9. jar944

    jar944 Been here awhile

    Joined:
    Aug 2, 2010
    Oddometer:
    751
    Location:
    Chantilly VA
    Hopefully this solves the plumbing problem, I made it the 90 a interference fit to the down tube so i dont *think* I'll need to weld it.
    [​IMG]
    [​IMG]
    [​IMG]
    #9
  10. jar944

    jar944 Been here awhile

    Joined:
    Aug 2, 2010
    Oddometer:
    751
    Location:
    Chantilly VA
    I didn't like the design of first one I made so I machined another 90 degree adaptor.
    [​IMG]
    [​IMG]
    [​IMG]
    #10
  11. VxZeroKnots

    VxZeroKnots Long timer

    Joined:
    Jun 5, 2008
    Oddometer:
    2,944
    Location:
    Durango CO
    awesome! :clap

    I'm digging the asymmetrical frame and machining. Be sure to post lots of pics with the updates!
    :beer
    #11
  12. jar944

    jar944 Been here awhile

    Joined:
    Aug 2, 2010
    Oddometer:
    751
    Location:
    Chantilly VA
    Thanks. I'm almost done with the chassis conversion mods. I only have to machine the SXF swingarm to fit and i'll be done.

    Then I can start on my other hybrid.
    #12
  13. jar944

    jar944 Been here awhile

    Joined:
    Aug 2, 2010
    Oddometer:
    751
    Location:
    Chantilly VA
    I ended up making line boring arbor for the swingarm, as it needs machined to fit the RFS motor.
    [​IMG]
    I tried just using a Drill to spin it but I had too much chatter. I ended up just chucking it in my lathe and using the carrage to push the swingarm into the tool bit.
    [​IMG]
    [​IMG]
    completed swingarm
    [​IMG]
    #13
  14. jar944

    jar944 Been here awhile

    Joined:
    Aug 2, 2010
    Oddometer:
    751
    Location:
    Chantilly VA
    The frame mods are done, and everything has been mocked up.

    [​IMG]
    [​IMG]
    [​IMG]
    #14
  15. BRYANDENNY71

    BRYANDENNY71 Been here awhile

    Joined:
    Sep 24, 2010
    Oddometer:
    118
    Location:
    Garden Grove, CA, USA
    I understand all of perks of the RFS motor......but the RFS bikes dont handle that bad.

    & 600-613cc RFS????? You are boring & stroking the thing too???

    My '06 EXC handles pretty damn good. Good enough for me & I'm an ametuer/intermediate class desert/GP racer.

    Although I do wish I had the SX suspension on it because then my suspension guy could work major wonders (he's KTM's factory supercross suspension mechanic).

    Are you really good enough to benefit from all of this?

    With the amount of time & money you've put into it you coulda bought a spare RF4 motor. haha.
    #15
  16. jar944

    jar944 Been here awhile

    Joined:
    Aug 2, 2010
    Oddometer:
    751
    Location:
    Chantilly VA
    They do not handle nearly as well as the SXF bikes, additionally the pre 05 framed bikes are even worse.

    Yes 99mm (+4mm) bore and 78mm (+6mm) stroke

    Yes, If from nothing other than the susp upgrade alone. significantly stiffer frame makes a noticeable difference as well.

    I'm generally good on spares...
    [​IMG]
    Though I have less in the compete chassis than what I paid for my spare RF4 motor.

    Also this bikes primary use is hillclimbs (Reasoning behind the 600cc motor) not my race bike, I have a 450sxf and yz250 for that.
    [​IMG]
    #16
  17. BRYANDENNY71

    BRYANDENNY71 Been here awhile

    Joined:
    Sep 24, 2010
    Oddometer:
    118
    Location:
    Garden Grove, CA, USA
    If its just getting used for hillclimbs....then why all the trouble for a little better suspension & a little more rigid frame?

    You dont really need all of the perks if its just for hillclimbs.

    You're putting make-up on your butthole. hahaha.

    All in all I actually like the concept. Thats why I'm so leary of getting rid of my '06 in lieu of an '11 or '12. I'm thinking of just investing in the SX suspension, getting it dialed & just riding it til it dies. Then rebuild it.
    #17
  18. VxZeroKnots

    VxZeroKnots Long timer

    Joined:
    Jun 5, 2008
    Oddometer:
    2,944
    Location:
    Durango CO
    Good work man, it is a neat undertaking if only for the curiosity of having a project. If I had all those tools and frames lying around I'd start building frankenstiens for the hell of it, if only to irk people like the poster above.
    #18
  19. jar944

    jar944 Been here awhile

    Joined:
    Aug 2, 2010
    Oddometer:
    751
    Location:
    Chantilly VA
    It's the same concept as putting a Cr500 in a gen4 CRF chassis.

    have you ridden a SXF/XCF?
    #19
  20. jar944

    jar944 Been here awhile

    Joined:
    Aug 2, 2010
    Oddometer:
    751
    Location:
    Chantilly VA
    Carb to headstay mount clearance
    [​IMG]
    [​IMG]

    RFS to SXF plumming
    [​IMG]
    [​IMG]
    [​IMG]

    gen 2 carb w/ wr426 rear bell to 530 carb boot
    [​IMG]
    [​IMG]
    #20