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tpgsxr750

2003 WR450 Motor in 250 Aluminum Chassis

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I have an 03 wr450 that I'd like to put into an aluminum chassis. The 450 aluminum chassis seem to be much more difficult to find and much more expensive. Has anyone else tried this project? How much modification to the frame is required to make the 450 motor fit?

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I would think the mods would be considerable. Using a 450 chassis is already a big enough PITA that it simply isn't worth the trouble considering the cost of an '06 YZ450.

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I thought about something like this for a 426. You have to consider a lot of things. Subframe, triple clamps, swingarm, your exhaust will have to be custom fit most likely to the subframe, your front mount motor bolts will have to be custom built, check to see if your master cylinder will fit ... These are just a few .... Their are so many things you have to consider and once you have, you will see it's a hell of a lot cheaper and a lot less headache if you just buy a newer bike.

(for my case) Even if you say you did it for California green and red sticker laws the DMV sticker goes by your frame ... not the engine. So if I swapped my '02 motor (green sticker) into a '07 frame it would now be considered a red sticker bike (seasonal riding times)

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... your front mount motor bolts will have to be custom built, ...
To say nothing of the bottom motor mount point and the head stays. Then, there's the question of the oil supply....

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There are plenty of AF 450s out there that guys are letting go cheap. Putting a old motor in a new frame would be a PITA. Just my two cents.

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To say nothing of the bottom motor mount point and the head stays. Then, there's the question of the oil supply....

Do you have to move the bottom motor mount? I thought that one lined up ...

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Do you have to move the bottom motor mount? I thought that one lined up ...

We're talking about a 450 in a 250 2 stroke frame. I wouldn't bet on it. There's also very likely NOT enough room for the carb as it is, and the down tube split is higher on the 2-stroke, so it may interfere with the header.

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I should have clarified, I did mean a 450 four stroke motor in a 250 four stroke aluminum chassis. I'm posting this for a friend of mine and he''s told me that there are very few 450 aluminum frames floating around and the ones that are are 3-4 times the cost of a 250 frame. I was talking to him about the conversion and he seemed to think that aside from the frame, subframe, rear suspension linkage, and possible the motor mounts everything else should bolt up. I wanted to see if anyone else had attempted this mod either with a 450 or 250 aluminum frame with an older motor to see if they could verify the parts bolting up and whether or not it's worth the headaches. His current 03 motor has been completely rebuilt but his frame and subframe have taken 300 or so hours of abuse and while he loves the motor he figured he could drop a few pounds and put himself in a fresher chassis.

Thank You to everyone that's posted.

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... he figured he could drop a few pounds ....
He's wrong. The aluminum YZ450 was 1 pound lighter than the steel '05 model. The frame is not about weight.

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So his plan is to lose a pound and upgrade to a better frame that doesn't have the stress cracks that his current bike has. Like I said before, I'm not the one contemplating the swap, just trying to get some info for a buddy. Thank You

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