Are CDI boxes interchangeable? That is to say, will a CDI box from a 300ex work in a 250r or vice versa? Or do they have to be from the model they are made for? Thanks.

 

i think they have to be for the same engine size at least because i have a 86 trx 250, an 94 trx 300 and an 02 400ex and the cdi's wont work on the 300 from the others. i currently need a new cdi for my 300 thats why i tried. my question here is will a 300 ex cdi work on a 300 utility because it is the same motor if i am not mistaken? i have a chance to get one for a 300ex cheap so i need to know any help would be great.

 

More often than not they are not interchangable. Get the right box for the right machine.