building a custom trailbike: Honda CRF chassis + XR250R engine

XR200/230 swap would be a piece of cake. That engine is great in my CR80, but wanted a little more power in the bigger CRF chassis.

Was tired of owning/maintaining 250F's, but KTM XC4's have proven reliable enough that this project is harder to justify. Still kinda cool, like the idea of a bike I shouldn't ever have to do more to than change oil and tires.

I havent tried myself.

Un-deterred by the XR 250 engine being a No-no I've picked up a cheap Suzuki DR 200 . Pulled engine, dropped straight into the crf 250 chassis, held off only by the lower rear engine mounting. Removing this will allow engine to sit where it needs to and at the right attitude to keep oil level the same. Drive train lines up lovely, plenty of room to swing the kick start and room to fab up a air of mounting plates to hang off the original frame mounting lugs.
i'll try to sort out pictures in the next day or two and keep up the posting as it comes together.
The DR200 does not use oil in frame or an oil cooler, this again simplifies the transplant. OK, it's not going to rip your arms off in 1st gear, but it's a bullet proof little air / oil cooled unit in a modern chassis.... ride it, put it in the shed, ride it, put it in the shed, ride it, I'm sure you see......and change the oil / filter once a year.

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looks like I've had some success with the photos.
You'll notice the notch in the top horse-shoe shaped rail, this was where I'd previously put the XR250 engine in, not needed for the DR200 motor, but it does make it easier to get it in and out. Having ground off as much of the rear lower engine mount as I dare (without splitting the motor), it still won't go back far enough to line up with the swing arm pivot bolt. minor Surgery required to the rear cross member of the cradle frame, i'll add photos when I've cut it away. this is the only area that needs mods, the front engine mounts line up nicely on chassis and engine. so a couple of plates needed either side at the front. and i'll possibly remove the lower frame mounts.
the only other thing that clashes is the oil drain. again i'll add a photo to show this, once I've got the swing arm pivot through the top rear engine mount. i'll need to bush the frame on both sides. the swing arm will need minor mods too. machining the gap between the arms wider and making new bushes with reduced I.D. to suit a smaller swing arm pivot bolt (the original from the DR 200 fits)

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Just a couple of photos of notching the alloy frame, nice garage bodge showing for some things you can manage with the machine shop.

Further frame surgery, I've cut away some of the rear lower cross member of the cradle, still need to tidy up this area and grind a little more away to fab back in. Still need to notch out the frame for lower right casing slightly and the oil drain on the lower left. i'll remove both lower frame mount brackets and add two more higher up when I patch back in the frame tubes and add some reinforcing to areas I've reduced.
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Feeling a bit like I've hi-jacked the original thread here, but it's all CRF rolling chassis related. There's probably an engine that would drop straight in with no (or minimal) frame mods, if any-one knows of one...Pitch in !!

cool that you are tackling your own "ultimate trail bike" build

not cool that you're clogging up someone else's thread, start your own thread for your own build, its better that way.