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Old 03-30-2011, 02:21 AM   #1
jesusgatos OP
fishing with dynamite
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Joined: Nov 2006
Location: on the road
Oddometer: 2,414
building a custom trailbike: Honda CRF chassis + XR250R engine

I killed my WR250F a few years ago riding Gifford Pinchot (totally worth it) and although it was a fluke thing and wouldn't have been much work to fix, I was over it. Just don't like having to deal with the maintenance that those small-bore 4-strokes demand. So I thought about buying a 2-stroke. Something like a KTM 200, or a YZ250 set-up for woods riding. But, well, I like building things and what I really wanted to be riding was an updated XR. Something like an XR250R engine in a modern chassis. Air-cooled, stupid-simple, reliable engine with a good chassis, suspension, brakes. Dwight Rudder started a thread on thumpertalk on this topic several years ago. He decided to build a customized CRF230. The CRF230 was appealing because it's based on the XR200 engine, and has a 6spd and e-start. But the XR250 also has a 6spd, has a 4-valve head, and makes a little bit more power (16 vs. 20 stock, according to info I read online). The '96 and newer XR's are dry-sump engines, and are a little bit more compact than the earlier XR250 engines. Found this image somewhere online that illustrates the differences.

So I started shopping. Watched the classifieds and found a clean 2000 XR250R. Bought it. Pulled the engine and sold the bike. Started taking some measurements and it looked like it would almost bolt right into my 2003XR250F chassis. Had just blown-up the engine in that bike, so I was tempted. But that Yamaha wasn't a particularly great-handling bike. Found out a few months later that one of my buddies had just blown-up his CRF450R while he was riding in Mexico. Called him. Hey sorry to hear about your bike, but, um, what are you gonna do with it? He thought I was nuts for wanting to put an old air-cooled XR engine in a racebike, but was happy to be rid of it.

Took a few months to get it from San Diego all the way up to Bend, OR, but I tore into it as soon as I rolled it into my shop. Checked a few critical dimensions, and it looked like a good fit. Would have to cut the engine cradle out, but that was no big deal. Took me less than a day to get it stripped-down and cut apart. And there it sat. Got pushed aside (literally) to make way for another project. Decided to pack everything up and hit the road. Spend some time traveling. But first I was going to build a custom motorhome out of an old 2.5-ton military 6x6 called a deuce and a half. Took this picture right after I brought home this water-damaged camper to strip a few appliances out of (vintage stainless steel oven/stove). That's my buddy Duane, and I think he was saying something about what a hillybilly I am.

Been several years now since I 'started' this project, but never really did much more than collect a bunch of parts. Motorhome is coming along slowly-but-surely, am almost finished rebuilding my desert truck, and don't know... just seemed like it was time to get back to work on this bike. Making time to work on this project in between all my other projects though, so it's going to be mostly nights, weekends, and rainy-days. But I'm motivated and this is actually a pretty straightforward deal. Made some space in the garage today and got started.

Not a bad fit. It's sitting in there cock-eyed because I have to clearance the frame and I'm doing that with a die-grinder a little bit at a time so I don't remove any more material than absolutely necessary.

The twin-spar frame clears the head with plenty of room to spare and should make working on the bike pretty easy.

Stock gas fits too. Am planning on putting the bike back together with the stock tank and plastics (minus the radiator shrouds) to see how it works, and if I like it, then I'm going to make a new tank, subframe, seatpan, and plastics. Already have a pretty good idea of what it's going to look like and it's gonna be sexxay.

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