I recently purchased a 89 250r that has a arens chassis, I am interested in installing a 400 ex motor into it. Will the ex motor bolt up to the motor mounts already there, if not does anyone make a kit to do this switch,
thanx

 

i'm pretty sure it's a really easy bolt up, maybe a lil modifyin, but i'm not sure, you need to get a reply from someone that has done this b4,, by the way,,why do you want to replace the 250R engine with a 400ex engine????

 

I race moto cross and I already have a 2 stroke machine.. a shee. I am dominating that class at my local track right now and I would like to branch off into the 4 stroke class as well. The r i bought is pimped out big time except the motor so I figure on putting a built ex motor in it and bam I'll have my 4 stroke racer.
Any more replys would be appreciated.

 

It won't fit correctly. First of all the swingarm pivot on a 400ex is also the rear motor mount. Secondly the 400ex is much higher and wider. All of the aftermarket four stroke frames have wider top frame rails so the four stroke will fit properly.
If the quad you have is in good shape, don't butcher it up. Chances are you can rig some mounts up to make the engine fit, but unless the engine is located properly it won't handle properly.
If you are sure you want a 400ex , the best thing would be to sell the frame you have and buy an aftermarket 400ex frame.
You shouldn't have any trouble selling an aftermarket 250r frame and all of your bolt on parts should go right on the new frame.