Ok so doing the final touches on the (very annoying) EXUP valve on my FZR400 (3EN2) today, I decided I might as well pull out one of my FZR250 (3LN3) ones and do a bit of a comparison. Don't know if it's ever been done but considering these things frequently wear out for us hard working Yamaha owners... the question might be asked if they are interchangeable (and if not, what parts are). So here you go: 1. The "valve" itself. You will notice that they are EXACTLY the same in all dimensions except for a groove on the outer shaft on the FZR400. I have no idea what that groove does, as the assembly seems similar, maybe others might know. The bushing sizes are therefore exactly the same, and you could interchange this part if need be (or retrofit bushings across etc). Note on the second photo it looks like the FZR250 might have the flat sides of the shaft different but it was just leaning on an angle for the photo. The flat sides are in the same position on each valve. 2. The outer plate. Unfortunately these are different, you can see that the alignment holes for whatever reason are offline and they are a different shape so you couldn't change these over. I have no idea why Yamaha did this, the thing serves exactly the same purpose so they could have made them the same. The bushings in the holes are the same size, the 400 is just worn more. There are two in there, a little metal one and a graphite one. I knocked them out of the FZR250 hole to see what they were, I actually retrofitted the graphite one to the inside shaft of the 400 valve... it fit so happy days! ...and no, drilling out the holes won't make it fit. I didn't drill but I test fitted and I highly doubt you could make it work. It's because the flat side at the top of the first photo - much more level/square on the 400 meaning the alignment with the exhaust header is awkward if you cross fitted the 250 (or vice versa) 3. The cable attachment. Photo speaks for itself, you'll see the 3LN has a different rotation on the shaft position relative to the cable holes so you can't change this part either (it would fit because it's physically the same size but your air flows would be off). Hope that helps others.