KTM RFS/SXF Hybrid

[LukasM]

Bump for a very cool thread that is not getting the attention it deserves!

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.

[renogeorge]

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

[LukasM]

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.

[jar944]

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.

[jar944]

latest hybrid

[dentvet]

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

[jar944]

Originally Posted by dentvet

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

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

[jar944]

I made a deal for a 637cc cylinder over the weekend, so now it should be largest cc hybrid out there.

[Foot dragger]

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.

[jar944]

Originally Posted by Foot dragger

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.

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.

[blake716]

Awesome thread!

[KTMandu]

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.

[LukasM]

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.

[KTMandu]

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.

[LukasM]

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.

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).