Are the parts interchangable. Will a 300ex stator work on a Honda 250X?

 

Don't see why not, the only difference between the two is electric start on the 300, so it may have a higher output on the rectifier side to charge the battery, so you may end up with brighter lights at idle. Shouldn't be a problem, but I'm no expert, so if nothing else, a quick call to a Honda dealer should get you the info.