Motor Swap

xiondavis

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Not really - the CRF250frame has more ground clearance and the motor sits a bit higher. The 450 cradle is wider, so none of the mounts will line up. The 450 motor has upper mounts where the 250 does not. You could make it fit, but you would have to heat a bump into the tank and the 450 torque would probably crack the lower motor mounts by not having the upper motor mounts. Not sure about the rear swinger mount - I don't have a 450 at the shop right now, but I think they looked similar, i bet the 250 is narrower than the 450.

Depends on why you want to do this... pre 2005 crf450 frames are not too hard to find. You can pick up a decent older complete CRF450 for around $1200. Normally they just need valve shims and a set of rings (on the cheap). Most people don't rev out the 450's like the 250s, so valve issues aren't so much of a problem.

If you are looking for a smaller bike, The 2005 and later frames feel a lot smaller (the 2004 crf450 feels like a tank compared to a crf250, but the 2007 crf450 feels pretty light. A lot of the difference between 250 and 450 is the motor - a 450 motor is a LOT heavier than a 250 motor... you will not be able to keep the light feel of a 250 if you swap in the 450 into the 250 frame.
 

steelman

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I currently have an 05 CRF250 with some upgrades. I want a 450 and have access to salvaged bikes. I was just thinking about a swap, before I spent the $$ to purchase a 450.
 

xiondavis

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If you try the swap, post some pics... If you have access to salvage 450, you can just grab a frame and swingarm too, nearly all of the other parts are interchangable, although your springs will be a bit soft for the weight of the 450. Checkout thumpertalk if you need some info... or you can check out bannedcr500riders.com for cr500 swap info - they wedge cr500 motors into the crf 250's

My wife races a CRF250r - she complained about keeping up with my brother and I in the dunes (he has a kx500, i ride a CRF450r). We tried putting her on a 450, but she is really short and we like to keep her bike as short and light as possible with a smd subframe kit and trimmed seat + i alread invested in her suspension. I ended up buying her a used athena 280 kit, (with a hotcam to bring the top end back), then we geared it up a bit for top speed. She can almost keep up now (In the desert, i'll be in 4th cruising, and she is 5 gear topped, but we don't leave her behind anymore :)
 

SnowFarmer

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Not without serious modifications to the frame and gas tank. Lower spars and down tube.
The 450 Frames are built around the motor and suspension for that power and torque. Conversely the same with the 250. Not saying it can not be done. If you have the time and the ability.

Note. The 02-04 450 motor mounts are the common I believe. 05-06 common,
07 different 08 different yet.

Try ebay or you could try Service Honda or any of those shops that make hybrid 500's.


Do you every share your access to salvaged bikes? Looking for some extra wheels and misc. parts.
 

steelman

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Not without serious modifications to the frame and gas tank. Lower spars and down tube.
The 450 Frames are built around the motor and suspension for that power and torque. Conversely the same with the 250. Not saying it can not be done. If you have the time and the ability.

Note. The 02-04 450 motor mounts are the common I believe. 05-06 common,
07 different 08 different yet.

Try ebay or you could try Service Honda or any of those shops that make hybrid 500's.


Do you every share your access to salvaged bikes? Looking for some extra wheels and misc. parts.

I think I will just upgrade to a 450. I have a buddy that is in the Auto Salvage business, so when he goes to Auctions, he picks up what is there. Let me know what you are looking for and I will see what he has. Thanks to all for the feedback.
 
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