CRF450 motor in 250R frame??

[Evan]

Has it been done? I am thinking about doing it, the old R motor aint cuttin it for me. I am thinkin it will be a lil funky with the bottom motor mounts and gettin the airboot to fit right. Seems like it would work better than in a 400ex frame, as the R frame is narrower, so the kick start would work better, and already has mounts for a rad. I know i need a larger rad. to cool the motor. What else...?

[EvilJester400EX]

bump

[250rmike]

i asked this a while ago. the only problem i could see is getting the motor to fit in the frame cause its so much taller than a r motor and there isnt much room above the r motor anyway. for the airboot you could use some flexible hose like from a vacume(sp?)

[Evan]

Well, from studying pics, heres what i gathered.
Airboot shouldnt be to much of a problem, the aftermarket frames use the stock airbox and appear to be in the stock location. I will proably need to have new spacers made for the s-arm, that shouldnt be to hard. I have a stock length 86 s-arm so that will help keep the front end down with the 4stroke hooking so much-I belive they are the equivalant of a +1 s-arm on a 400ex and thats the hot setup for 400s. I am somewhat undecided about the top motor mount, Im sure we can make something once we get it in the frame and look at it. The bottom mounts appear to be in front of the stock R motor mounts so we can make new bottom mounts and leave the R mounts alone, this way I can switch out the R motor and have crf motor, or vice versa. The Front motor mounts shouldnt be hard to make at all, I have a freind whos made them b4 for a yz conv. I will def need to upgrade the radiator, as it wont be large enough to cool the crf. New hoses for the crf as well. I am not sure on the kickstarter, from what I have seen, no extension is used, if there is, i guess we will have to buy one. Shifter.. I dont know if it will clear the frame, most of the aftermarket frames it clears fine. If I am to run the R motor, I will proably need another s-arm since my stocker will be modified. Anything Im leaving out? A flip top seat would be cool.....

I forgot about the pipe, I have no idea what to do about the pipe, suggestions? Alot of people use the TC, but I dont like how that pipe is cheaply made, Id rather have a Sparks if it would work.

[sweet300ex]

i think the 250r frames are too low to the ground, and thats why most ppl put them in modified 400ex frames or aftermarket ones

[cody anderson]

good luck dude... don't do it!!!!!!!!!!!!!!!!! it will be a nightmare! people dont put them in a 250r because the frame rails are too close to each other. (top and bottom) they use an ex because they are farther apart since 4 stroke motor came in it originally. plus you can use the motor for the pivot point for the swingarm.

[Tommy 17]

i know someone that asked john arens if they could mod their arens 250r frame to pu tin the 250r motor and he said it won't fit... that they have to use a 400ex style frame...


but lsr, laeger, walsh etc are all 250r style:huh

[Taco]

crf motor is too tall for the R frame

[250rmike]

yes finally a couple of people accually agree with me on something