XR400 Cafe Inspired Project

settintrendz

Adam Berg
I grew up in the dirt. Riding and racing motocross and bmx. The passion I have for building and riding bikes is generations-deep. Inspiration for the crap I like to build comes from just about every genre of two-wheeled racing, but Id have to say, as evidenced by the thread title, mostly the dirt side of motorsports.

Im mildly obsessed with small-bore, air cooled, vertical Honda motors (XR75/80/100). Not because they are amazing machines with great handling and loads of power (not even close), but because its fun to try and make them go much faster than they were ever intended or should for that matter. Plus, just about everyone that rides (dirt or street) has had experience with, or may have even learned to ride on one of these little guys. They are wildly fun. In fact, we build hybrid mini motocross race/play bikes for adults around the XR/CRF100 motor with a modified CR85 chassis and parts.

Why all the blab about these turds?

Well, while designing/building an XR100 for the salt of Bonneville (in a sort of café style), I thought... Why not build one for the street, using its big brother, the XR400? It fit all my ridiculous requirements; Air-cooled, single, Honda, and I already had the bike.

Few of the specs:
-Honda XR400 motor (440 kit/cam/custom clutch set-up/ machined flywheel/ etc)
-Custom one-off frame
-Sportster front forks, re-sprung and valved
-Mono shock, custom motocross style swingarm, Showa shock re-sprung and valved
-58" WB
-26 degree head angle/ 3.25" trail
-18/19" custom wheelset
-Custom rotors/ Wilwood calipers
-Hand-formed aluminum tank/ tail/ fender

I know its stupid, but here goes...

Quick little sketch of the basic, overall idea.



And here it is in full scale 1:1



Let the fun begin









 
Frame taking shape











Comparing those last 3 pics with the following, you'll notice a couple modifications. 1) I took a couple inches out of the overall length so it fit tighter around the motor. 2) I raised the wishbone/ seat spars where they meet the top tube for better clearance around the carb.





 
Sounds like a very interesting project, look forward to seeing the transformation.
 
I'll be the first to say I was skeptical at first just based on your user name. Like oh God, here comes another boner thinking he's about to change the "scene." Well...we aren't there yet but I have a strong suspicion I'm going to stand very much corrected on my that. You obviously have a solid foundation in mechanics, a well thought out vision, and the wherewithal to take those two assets and make something very unique and functional. 100% on board with this, awaiting updates.
 
Thanks to those who have an interest in this ridiculous project. :p
And to address your comment, coyote13, the only thing more ridiculous than an XR400-turned-cafe(ish)-racer, is indeed, my username. SettinTrendz is the name I chose for my business when I started it 17 years ago. I thought that was really cool when I was 18 y/o. I was wrong. haha. As we began to develop a reputation and considered changing the name, we thought it might just confuse folks. Anyway, We build high-end hot rods and muscle trucks, and the name has stuck these years. Funny thing is... Those who know me best, know that I despise "trends". Even if we ever are on the leading edge of some part of our little world, I would hope that whatever design were putting out would be thought of a simple and timeless.
SettinTrendz has now become my username for the few forums I frequent, almost as a jab to myself. Makes me smile.
 
Well kudos to you sir, that's a great self assessment. You should post up some of your shop's work, I'm sure some guys on here would love to see some classy rods.
 
coyote13 said:
Well kudos to you sir, that's a great self assessment. You should post up some of your shop's work, I'm sure some guys on here would love to see some classy rods.

Will do. Ill have to find the most appropriate section I suppose.
 
Really like the coincident swinger pivot and engine mount. Any chance we could see how the assembly works? I'm presuming the engine (or at least its mounting bushing) is rigidly bolted to the frame, so I am wondering what sort of bearings/bushings and shimming you are using for the swing arm. Looks like it could be a bit tricky to get it all together and shimmed properly, but its great how close the pivot is to the drive sprocket. Is this the original scheme used for the XR?
 
Back to the project at hand...

This is the fine specimen of an MX swinger I have chosen. It began life on an 87 CR125.



I started by chopping the linkage mounts off, then widening it by .625". What you see welded here in the center ended up wrapping all the way around the cast section to hold the space while in the fixture.



Then I boxed the entire cast section and added the hoop/shock mount.



 
jpmobius said:
Really like the coincident swinger pivot and engine mount. Any chance we could see how the assembly works? I'm presuming the engine (or at least its mounting bushing) is rigidly bolted to the frame, so I am wondering what sort of bearings/bushings and shimming you are using for the swing arm. Looks like it could be a bit tricky to get it all together and shimmed properly, but its great how close the pivot is to the drive sprocket. Is this the original scheme used for the XR?

Yes, it is the original design of the XR, as it is with most off road/ motocross bikes due to the high travel numbers. And yes, the motor is solid mounted in the three points outlined above. Like you said, sprocket close to swing arm pivot. That of course limits chain slider wear as well as keeping chain tension fluctuation to a minimum, without the use of a tensioner. And although the swingarm I used is not an XR unit, it works the same way. Ill take a close up pic of the bearings/ sleeves/ seals the next time I have it off.
 
Whoaa! this thing is awsome... Very nice fabrication sir! I will be following along!
 
Very impressive work so far. Another Honda single lover following along.
 
Thanks fellas.

Need to start the bodywork so I can get my control placement nailed

Some chipboard cut-outs to get an idea of what I want. And a little shaped foam for dimension on the tail.









 
Ive been tossing around two different ideas for the bodywork.

If you look at the original quick sketch you'll see that theres a lot of shape to the bottom lines of the tank and tail. For quite some time, I thought this is what I wanted.



Ive gone back and forth on the subject, but now, seeing it in three dimension, I really think it needs to go on a diet.

A straight line from the bottom front of the tank to the back of the tail is what I was trying to get away from. Im now really warming up to it.







Starting to tuck-shrink the top of the tail section on the stump





 
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