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XR650 motor in an XR400

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Anything is possible. Was it designed to fit? No.

I'm not sure exactly how much cutting and welding would be required, but certainly a good bit will.

I really am just guessing here, but I imagine an XR500 might be a better fit. Maybe you can just upgrade the 400 to have more displacement and better air flow.

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Probably like the 350,,looks like a 600 will fit until you actually try it,,then reality strikes.,

How do I know??,,Purchased a 350 frame which was advertised for sale as a 600,,I bought the thing and discovered it wasn't a 600 frame when I tried to put the 600 engine in it.,Looked the same,,but no, it was sort of close but no cigar.,

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go to your local honda shop with a tape hopefully they will have both models start taping from the countershaft in all directions up down ba ck forward then see just how close the measurements are, most critical are from the countershaft back and up the 650 is a compact motor for a 650 and the 400 is big for a 400 so you might no be too far off let us know how it goes, Ive been looking at the 650 myself for my avenger chassis in case my 430 lets go. I dont think you will have a problem with the radiators just have to weld on the mounts and use a tank from something that came with radiators hopefully not the 650 (they are ugly)

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What's the point?

I agree, why would you bother. The 400 is so close in physical size that I see no reason to even measure for a possible fit.

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it only makes sense to do this if you have a 400 with a blown motor and a really cheap 650 motor, I would really like to see someone do an avenger with the 650 motor as they have a smaller chassis than the 400 and are much lighter and they are made with a quality chrome-moly frame

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Can this be done?! Please give me some advice

Is it a 650r or L motor? I just built a xr440r in the begining of the year, now I'm doing my xr600r and with out the bikes right next to one another the 600r motor seems considerably larger... or alreast it feels that way...

I've thought about fitting a xr400r sub frame on the 600 to mount the plastics and seat. Not sure about the air box though... Currently i dont have a budget for cosmetic improvements.

Why you ask? Why not? Lets see some pics and fab work!!

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650r in a 450x frame I would like to see.

Me too!! What kind of power can you get out of a 650r motor compared to the 450r motor? A hot 450 will make near 60 wont it? I'm getting that number from Jeff Emigs spiel when the outdoors was in Co.

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Me too!! What kind of power can you get out of a 650r motor compared to the 450r motor? A hot 450 will make near 60 wont it? I'm getting that number from Jeff Emigs spiel when the outdoors was in Co.

that is the right question but it is not about peak hp its about quality power off the bottom not having to wait until 3 or 4 grand for serious power and then have it it hit to fast to be controlled, being able to shut off on a steep hill then just roll back on without stalling, with its 80mm stroke the 650 will always have an advantage in those types of situations but it will always be heavier even if put in a 400 or 450 frame, about that have you ever tried getting a 450 back in its own frame, major rubicks cube sold mine right after I got it back together, however if I were to put on in my avenger it would come out somewhere around 233 lbs hmmm,

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looks like a lot of work wish him well but somebody should tell him that his motor is setting to high in the frame he is likely to have chain problems when he bottoms the suspension.

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the cradle is already cut out , but if you look at the pictures closely you can see that the countershaft is level with the top of the swingarm , what will happen when he puts the sprocket on is that the chain will not be level with top of the swingarm, as the arm moves though its arc of travel the chain will contact the bottom of the swingarm and try to saw it in two, been there done that,

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I have to agree with moto on this one if you are talking 450 or 400 chassis at best it is just a giant jump sideways at worst you are messing up two pretty nice bikes and throwing resale out the window to end up with something not as good as either, but with a chassis kit you will end up with bike alot lighter than the stock 650 handling will be better if you know how to setup (big if there) but if you just got to be different just do what you want and have fun

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the cradle is already cut out , but if you look at the pictures closely you can see that the countershaft is level with the top of the swingarm , what will happen when he puts the sprocket on is that the chain will not be level with top of the swingarm, as the arm moves though its arc of travel the chain will contact the bottom of the swingarm and try to saw it in two, been there done that,

Right in the 450x frame... I was talking about the 400 frame....

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that makes more sense now, the 400 would be a much easier swap than the 450, and I think the chassis is a little more compact than the 450 (shorter wheelbase and lower seat height) who knows might even be lighter? maybe somebody has weighed them both

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