250r with trx450r motor?

[400man]

has anyone here tried building a stock frame 250r using a honda trx450r motor? it seems to me that it would be a pretty simple swap, just make some new motor mounts and other little details. how much difference is there size and dimension wise between the 250r and 450r motor?? I think it would make a awesome custom woods machine.

[250x_kyle]

it would probably destroy a 250r frame.

[dehner47]

:rolleyes:

dont think it would destroy the chassis. you gotta remember, the stock 250r chassis may not be industructable, but is one of the best chassis ever made. you might get a crack here and there just like ya do in the new chassis's. just have to put a few fish plates and gussets in there while building and you will be fine.

[usp4u]

Originally posted by 250x_kyle
it would probably destroy a 250r frame.

Awful proud of those trx motors ain't ya. add a few gussets and go town, all the while having the best handling stock chassis ever. As a matter of fact, it wouldn't hurt to add a few gussets to a 450r frame. ;)

[250x_kyle]

im not saying it wouldnt work with gussets. im just tryign to get at why chop up another stock 250r frame. and no im not awful proud of my trx motor infact my old hybrid had alot more crap then this 450r ever will.

[OutCast]

It's not like there is a shortage of 250r frames kickin around. I say go for it!

[250Renvy]

Originally posted by OutCast
It's not like there is a shortage of 250r frames kickin around. I say go for it!


Are you kidding? There is definitely a shortage of 250R frames. Most are beat and destroyed and repaired so many times because there is a shortage.

400 man - if you are going to do this despite people telling you not too, then please do it on a junkier 250R frame or at least an 86. If you take a mint frame and hack it up, well... I can't say what I think here and 89 frames are so rare that it's even more of a shame and for what?

Yeah the 250R's are good, but for 250R motors, a well built 450R will be just as good as a 250R with a 450R motor and everything fits better.

If you go to an actual hybrid frame then yeah the hybrid will be better because of the chromoly frame, but things will still fit better on the 450R, not too mention how cheap you can get them these days.

[mini]

crf450 will not fit "to tall"

[mini]

crf450 will not fit "to tall"

[250x_kyle]

Originally posted by mini
crf450 will not fit "to tall"

anythign can fit if you know what your doing.

[C41Xracer]

its not to tall, ive done this conversion before. its a very tight fit but i would never do it again it was a pain in the a**

[Jason Hall]

The problem with fitting a modern 4 stroke In the old R frame Is the top rear shock mount. It Is a main structure point of the frame, and Is right In the way of the carb. In order to keep the chain lined up correctly with the swingarm/slider the engine can't be mounted very easily.

I fitted a YFZ450 engine In my extra used and abused 88 frame, but had to do Major mods to the top shock mount. I used CRF450R linkage, and have since bought an aftermarket YFZ shock that was valved for my setup. The YFZ airbox and boot fit Very nice once the shock was mounted.
http://i237.photobucket.com/albums/ff42/Jasons450r/YFZ450RRRolling4.jpg

[Nahum]

... but had to do major mods to the top shock mount. I used CRF450R linkage ...

That´s interesting! It´s like the CR500 linkage. Can you show closer photos of the new upper shock mount? How did you find out where to weld the new upper shock mount (position, heigth, ...) Also: did you have to relocate the u-linkage mounts?