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Old 03-30-2011, 02:21 AM   #1
jesusgatos OP
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Location: on the road
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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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Old 03-30-2011, 04:09 AM   #2
crankshaft
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Very cool, I've often dreamed of the same project.
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Old 03-30-2011, 04:19 AM   #3
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Thats going to be one bad ass bike! I really like your Toyota truck as well.
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Old 04-01-2011, 06:02 PM   #4
jesusgatos OP
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Thanks guys, but you might want to hold off on the compliments until it's done. Lots of people take stuff apart and start these kind of projects. Hell, it's taken me over two years just to get to this point. Guess we'll see if I can finish this one in any kind of respectful fashion.

Next thing I need to do is figure out exactly where the engine needs to sit (side-to-side) because it affects how/where I have to clearance the frame. So I spent a few minutes taking some measurements and it looks like the distance from the centerline of the engine cases to the centerline of the front sprocket is within 1/16" from the centerline of the rear hub/swingarm to the centerline of the rear sprocket. So that means I can just mount the engine dead-center in the chassis from side-to-side. Not a big deal, but makes it a bit easier to locate and design/build engine mounts, etc.
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Old 04-03-2011, 06:15 PM   #5
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Just posted this on thumpertalk:

Quote:
Originally Posted by jesusgatos View Post
Am building a custom trailbike, putting an XR250R engine into a 2005 CRF450R chassis. Fitting the new engine right now, and would like to know where the CRF front sprocket is located, relative to the chassis. Would sure appreciate it if somebody could take a quick measurement for me. All I need to know is the height from the bottom of the forging to the centerline of the sprocket (pic shows measurement requested). Thanks in advance.

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Old 04-03-2011, 06:19 PM   #6
jesusgatos OP
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Have provided enough clearance to locate the engine side-to-side, but need to get a measurement for the countershaft sprocket before can do much more. Pretty sure am going to need to rotate the engine forward/down a bit more and that will require more clearance, but don't want to remove any more material than necessary.
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Old 04-03-2011, 06:31 PM   #7
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Sweet!

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Old 12-07-2011, 03:53 AM   #8
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Any updates? Sounds like a fun project.
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Old 12-07-2011, 08:38 AM   #9
jesusgatos OP
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Sadly, no. Have sold most of my bikes, and this was the one that I was keeping to travel with, but I've got my hands full with other projects (motorhome, mini-motorhome, XR600/650L scramblers, etc.). So I bought a 2010 450XCW to ride for now, and with the new Freeride 350 being announced, am not sure if/when I'll get around to finishing this bike. Kind of a shame, because it wouldn't take much. Guess I would consider selling it at this point if anybody wants to finish it? Send me a PM if interested.
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Old 12-07-2011, 05:14 PM   #10
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FWIW in the late 1990s there was a company in the PNW that built enduro-ized CR250Rs and their bikes carried fuel in the frame spars and in a specially-constructed skid plate with a compartment for fuel between the frame rails. I've also seen a couple of CRF450R supermoto bikes with oil in the front frame downtube. I have ambitions of modding my CR250R to carry as much fuel as I can manage in the frame, but don't know that I'll ever get around to it
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Old 12-07-2011, 06:17 PM   #11
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Quote:
Originally Posted by BikePilot View Post
FWIW in the late 1990s there was a company in the PNW that built enduro-ized CR250Rs and their bikes carried fuel in the frame spars and in a specially-constructed skid plate with a compartment for fuel between the frame rails. I've also seen a couple of CRF450R supermoto bikes with oil in the front frame downtube. I have ambitions of modding my CR250R to carry as much fuel as I can manage in the frame, but don't know that I'll ever get around to it
Cool, didn't know that. Was planning on using the downtube or the twin-spars to carry oil, as the stock fuel tank has plenty of capacity and there are really no clearance issues. Was going to run the stock tank to get it running, and then make a composite tank afterwards, mostly to smooth-out the lines (stock tank looks unfinished without the radiator shrouds).
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Old 12-07-2011, 07:26 PM   #12
DualSpaz
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Quote:
Originally Posted by BikePilot View Post
FWIW in the late 1990s there was a company in the PNW that built enduro-ized CR250Rs and their bikes carried fuel in the frame spars and in a specially-constructed skid plate with a compartment for fuel between the frame rails. I've also seen a couple of CRF450R supermoto bikes with oil in the front frame downtube. I have ambitions of modding my CR250R to carry as much fuel as I can manage in the frame, but don't know that I'll ever get around to it
I remember that. It was an article in Dirt Bike magazine. Although as I remember it, it was just some guy that had done it, not a product for sale. I think between the frame spars and the small compartment welded to the skid plate he got an extra .7 gal. It used a vacuum operated Mikuni fuel pump mounted to the skid plate, next to the custom fuel compartment. They did say it took forever to fill the tank(s).
Seemed like a good idea at the time.
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Old 12-07-2011, 08:00 PM   #13
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I think one of the build threads over at BannedCR500Riders has a guy using the frame for additional fuel capacity. That's a bike where you'd want it.
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Old 08-12-2012, 03:14 PM   #14
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It's been a while since I've updated this thread, and I've been too busy with other projects to dedicate any more time to this bike, but am looking forward to getting back into it. We sold off the last of our Hondas a while ago and I've got a big pile of parts left over. Got rid of the 450R suspension and have late-model CRF250X forks and shock now, along with a set of 20mm offset Scotts tripleclamps, which should make this thing really nimble. Also ditched the 19" rear wheel so I can run an 18" trials tire. The other thing I was really happy to snag was one of those old White Brothers E2 silencers off a 250F. It's got a one-piece can that's practically indestructible. Wish they still made 'em. Bunch of other small parts too. Forget exactly what, but have pretty much everything I need to finish this bike - except time, and motivation (my 450XCW kinda killed that). But I'm going to see this thing through. Eventually. In the meantime, check out this super cool thread on thumpertalk.
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Old 08-13-2012, 10:42 AM   #15
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Cool build! I like your Alaskan camper--I have one too lots of fun :)
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