KTM RFS/SXF Hybrid

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

  1. jar944

    jar944 Been here awhile

    Joined:
    Aug 2, 2010
    Oddometer:
    769
    Location:
    Chantilly VA
    I completely agree with you, but I don't think I said the RC4 motors were bad? The original list was specifically for the RF4:beer.

    The only reason I'm using a 250 frame (well 2 reasons) is that that are considerably cheaper and this one was (is) plated already. I have another 450sxf frame but it is titled as (off road only) and this build was specifically to be a dual sport

    Any of the new style frames should work (provided you add in a new cradle.) So someone could pick up a $150 150sx frame and do the same think if they wanted

    also my last post should have read 250xcf frame (you can see the spring mount for the kickstand in the pic)
    #41
  2. a1fa

    a1fa Throttle Jockey™

    Joined:
    Nov 1, 2006
    Oddometer:
    13,924
    Location:
    Arkansas
    :lurk mooooreeee
    #42
  3. GR0NK

    GR0NK Got some screws loose!

    Joined:
    Sep 24, 2006
    Oddometer:
    2,370
    Location:
    In the Valley of Bomb Runs...
    Yeah it was just the way the info was presented made it seem like "all" those KTM SX bikes have problem engines.

    I just picked up an 07 250 XCFW for my wife and she finished 2nd just yesterday in the women's class, first time on the bike! :D
    I finished 4rth Vet Master on the very same bike in back-to-back races after switching to it because I had "issues" with my bike. Motor aside, these frames handle night and day better than the RFS bikes. Yesterday's track was half MX and half tight woods. The XCFW is about 90-95% what my 200XC can do in the woods but (for me) it was much better on the high-speed outdoor MX style track than the 200XC, and that was with my wife's suspension on the bike. Realizing that the motor plays a big part in the handling, the new generation frames can climb out of ruts much better (like a two-stroke) and somehow do not exhibit the headshaking that some RFS bikes are afflicted with. I never once though it needed a steering dampener other than when knocking trees with the bars but when you're doing that anybody on any bike could benefit from a dampener.

    Like yours, our XCFW can be plated for street but short of complete catastrophic engine failure I don't think I could yank out the RC4 and replace it with an RFS. I am building a short-stroke RFS race motor so I may just need to find another frame to put it in. :deal



    Sean :bmwrider
    #43
  4. jar944

    jar944 Been here awhile

    Joined:
    Aug 2, 2010
    Oddometer:
    769
    Location:
    Chantilly VA
    Frame is done and painted, 90 degree adapter has been machined and installed.

    [​IMG]

    [​IMG]

    [​IMG]
    #44
  5. jar944

    jar944 Been here awhile

    Joined:
    Aug 2, 2010
    Oddometer:
    769
    Location:
    Chantilly VA
    #45
  6. LukasM

    LukasM Long timer

    Joined:
    Nov 15, 2006
    Oddometer:
    5,445
    Location:
    On a RTW ride - next stop USA!
    Bump for a very cool thread that is not getting the attention it deserves! :deal

    With my FE570 stuck in Chile for a few weeks it has motivated me to finally finish up the hybrid RFS/SX-F roller that has been sitting around for a year.

    Going to put in a stock 450 or 525 EXC engine, will be interesting to see how it compares to the Berg.
    #46
  7. renogeorge

    renogeorge Long timer

    Joined:
    Apr 7, 2007
    Oddometer:
    1,567
    Location:
    Reno
    I am interested in buying or building one of these. I have heard that none of the available aftermarket or KTM big tanks will fit, due to the tall height of the RFS motor. Anyone have any info on this? I wonder about the KTM/Acerbis tank which carries fuel forward in the radiator "shroud" area...

    Thanks
    #47
  8. LukasM

    LukasM Long timer

    Joined:
    Nov 15, 2006
    Oddometer:
    5,445
    Location:
    On a RTW ride - next stop USA!
    You should be able to modify most tanks with careful localized application of heat and a blunt object like a spoon.

    I know that people have done it with the 3.3 gallon Clockworks tank so I will probably get one at some point. They are reported to handle better than then same size Acerbis/KTM tanks.
    #48
  9. jar944

    jar944 Been here awhile

    Joined:
    Aug 2, 2010
    Oddometer:
    769
    Location:
    Chantilly VA
    The Acerbis fits (per crosscountrys thread) as well.

    I will likely be putting either the CW or acerbis on my 500 conversion, Though there it lots on space compared to a RFS on that build.
    #49
  10. jar944

    jar944 Been here awhile

    Joined:
    Aug 2, 2010
    Oddometer:
    769
    Location:
    Chantilly VA
    latest hybrid

    [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]
    #50
  11. dentvet

    dentvet Long timer

    Joined:
    Aug 4, 2008
    Oddometer:
    1,376
    Location:
    hunt country virginia
    Looks really tidy. Was it easier than the rfs swaps? How does the sxf chassis compare to the more typical cr500AF bikes? or your yz for that matter? awesome
    #51
  12. jar944

    jar944 Been here awhile

    Joined:
    Aug 2, 2010
    Oddometer:
    769
    Location:
    Chantilly VA
    It's a good bit easier than the RFS swap. Fitting the cr5 motor took no time at all compared to the tall RFS motors. The only frame mods were the motor mounts and pipe mount.

    I haven't ridden a 500af, however the sxf chassis handles very similar to the yz
    #52
  13. jar944

    jar944 Been here awhile

    Joined:
    Aug 2, 2010
    Oddometer:
    769
    Location:
    Chantilly VA
    I made a deal for a 637cc cylinder over the weekend, so now it should be largest cc hybrid out there. :evil
    #53
  14. Foot dragger

    Foot dragger singletracker

    Joined:
    Dec 27, 2006
    Oddometer:
    12,971
    Location:
    chico,just below rag dump(nor-cal)
    A friend had a basic Thumper 570 kit put in his 07 525 when it was time to refresh the engine. It ran fine for 8 or 10 hours, then out in the middle of nowhere the piston split exactly in 2 right in line with the wrist pin.

    Thumper has no idea,he has no idea,have you ever heard of such a thing?

    I like that CR500 conversion alot.
    #54
  15. jar944

    jar944 Been here awhile

    Joined:
    Aug 2, 2010
    Oddometer:
    769
    Location:
    Chantilly VA
    I've seen one do that (it may have been your friends if he posted on KTM talk though). I'm kind of fond of the CR5KTM myself.
    #55
  16. blake716

    blake716 nine toes

    Joined:
    Nov 5, 2008
    Oddometer:
    13,829
    Location:
    Baton Rouge, La.
    :clap

    Awesome thread!
    #56
  17. KTMandu

    KTMandu Adventurer Wannabe

    Joined:
    Sep 11, 2007
    Oddometer:
    333
    Location:
    Lafayette, LA
    Mr. Jar
    I've got a 06 400EXC and am contemplating putting this engine in a 07 SXF frame. Is this a worthwhile effort? Are the two frames that different? Old generation vs new generation.
    Will I have to cut the down tubes(yoke area) of the 07 frame to accommodate the 400 engine? All discussions seem to revolve around the 450 and larger engines. Externally, the 400 to 530 engines appear to be the same size.
    Will I need to relocate any of the engine mounts?
    Will the 06 swing arm, sub-frame and airbox fit on the 07 frame?
    I will re-read this post plus the related threads that you referred to(thanks for that) but some of the information therein is as clear as mud.
    #57
  18. LukasM

    LukasM Long timer

    Joined:
    Nov 15, 2006
    Oddometer:
    5,445
    Location:
    On a RTW ride - next stop USA!
    Just read this thread and all your questions will be answered 3 times over:

    http://ktmtalk.com/index.php?showtopic=375749&st=0

    FYI for all practical purposes your engine is the same as the tall 450/525 EXC and 525 SX so you will need to modify the frame significantly, either completely replace the lower cradle with the one from the RFS or at least redo the down tubes.
    #58
  19. KTMandu

    KTMandu Adventurer Wannabe

    Joined:
    Sep 11, 2007
    Oddometer:
    333
    Location:
    Lafayette, LA
    Lukas
    Thanks for the reply. There's a lot to read in that link.
    I don't know if doing this is worthwhile. I do not have the time, expertise or the machinery to tackle a project of this nature. Bums me out.
    #59
  20. LukasM

    LukasM Long timer

    Joined:
    Nov 15, 2006
    Oddometer:
    5,445
    Location:
    On a RTW ride - next stop USA!
    Try to bum a ride on a SX-F if you can.. although I did it without trying first as well and love the results. It handles a lot better than the RFS for sure, both in turning as well as high speed stability. Just hard for me to tell how much is the frame and how much is the newer suspension.

    If you can't do the welding yourself you can ask Savageya in the KTMtalk thread for the contact details of his frame builder, I bought it from him and it was very nicely done. Or maybe Jar wants to do it for a fee, he is the de-facto expert on the hybrid builds now. :deal

    The rest is just bolting stuff on if you get a frame with the newer bodywork/tank/seat/subframe and a 08+ EXC-R swingarm (I've got a spare if needed).
    #60