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Old 02-23-2011, 12:44 PM   #1
jar944 OP
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KTM RFS/SXF Hybrid

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/...tm-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.


dirt tricks got around this by machining a 90 degree adaptor for the t connector (as can be seen below)



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.









Yoke finished, lower mounts in:






More to come.

jar944 screwed with this post 02-26-2014 at 08:30 AM
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Old 02-23-2011, 12:51 PM   #2
BRYANDENNY71
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Why?
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Old 02-23-2011, 12:59 PM   #3
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Originally Posted by BRYANDENNY71 View Post
Why?
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.
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Old 02-23-2011, 01:05 PM   #4
LukasM
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Quote:
Originally Posted by jar944 View Post
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.


Watching this one closely.

Did you fix the frame somehow for welding or were you not concerned with distortion?
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Old 02-23-2011, 01:09 PM   #5
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Originally Posted by LukasM View Post


Watching this one closely.

Did you fix the frame somehow for welding or were you not concerned with distortion?
I kept the engine bolted in as much as possible during the welding/fitment.
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Old 02-23-2011, 01:38 PM   #6
dentvet
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lookin pretty good. Have you figured out what makes the new chassis better? I'd like to see the frames side by side.
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Old 02-23-2011, 04:38 PM   #7
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lookin pretty good. Have you figured out what makes the new chassis better? I'd like to see the frames side by side.
Rigidity.

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

250sxf 450sxf 560smr

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Old 02-23-2011, 06:14 PM   #8
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Why?
If you have the skill and desire, why not?

Looks cool, good luck!
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Old 02-24-2011, 05:43 PM   #9
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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.


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Old 03-10-2011, 08:31 PM   #10
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I didn't like the design of first one I made so I machined another 90 degree adaptor.


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Old 03-10-2011, 08:48 PM   #11
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awesome!

I'm digging the asymmetrical frame and machining. Be sure to post lots of pics with the updates!
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Old 03-11-2011, 12:13 PM   #12
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awesome!

I'm digging the asymmetrical frame and machining. Be sure to post lots of pics with the updates!
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.
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Old 03-12-2011, 06:03 PM   #13
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I ended up making line boring arbor for the swingarm, as it needs machined to fit the RFS motor.

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.


completed swingarm
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Old 03-20-2011, 05:25 PM   #14
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The frame mods are done, and everything has been mocked up.



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Old 04-05-2011, 10:27 AM   #15
BRYANDENNY71
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Quote:
Originally Posted by jar944 View Post
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.
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.
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