UNI filters come with a wire cage insert that supports the foam filter. This is meant to replace the very restrictive stock insert that comes on the bike from the factory.

Back when, I purchased filter NU-4126ST which was marked on the package as being for either the R or EX (interchangable), which was good for me because I have both machines. It came with an insert that had a TAPERED lip. This worked very well on the R, because the intake boot on that machine has a pretty steep taper. It did not work as well on the EX because it didn't have quite as much taper (although there seems to be a slight taper), but it was ok.

Alright, so later I purchase another NU-4126ST (also marked on the package as being for either the EX or R!), and it comes with an insert that is SQUARE and works great with the EX, but DOESN'T work on the R.

I look at the current UNI web site (http://www.unifilter.com/atv.htm), and they are now listing two different numbers for the R and EX. NU-4126ST for the EX (which I HOPE now comes with a square lip) and NU-4119ST for the R (which I HOPE now comes with a tapered lip). Please note that on the web site they have the years switched for the two bikes (98-04 for the R, and 04-05 for the EX), which is obviously a mistake (and doesn't inspire a lot of confinence!).

So, hopefully UNI has straightened out the issue of which bike gets which type of insert (???). If you have a tapered NU-4126ST on your EX, ditch it for a square one becasue it will seal much better. If you have an R you must use the tapered one, so buyer beware if you look at a package that is marked for both machines, and it has a square lipped insert inside.

(Note that my EX is old, and it is possible that its intake boot once had some taper to it, but over they years it has gotten flattened. In any case, the square insert works best for me now, and gives the best seal!)

 

It gets worse! Looking more closely, the NU-4119ST is also the filter listed for a bunch of utility machines. It is in fact the filter I run on my Ranchers (and it comes with no insert at all for some strange reason). Obviously this is NOT the correct filter for a 450R, so this is no doubt a catalog misprint along with the model years. And, the catalog now lists NU-4134ST for the Rancher (and again the wrong years for that model). Obviously the catalog is all messed up!!!

So, all I can conclude is that the NU-4126ST must have just come with two different types of lips on the insert at different times (???). In any case, you will have trouble carmming that square one into the intake of your R, but it does work well on my EX.

 

I think I now have the correct answers! The NU-4126ST is the correct filter and insert for both bikes, and the UNI catalog is all messed up. The collar on the insert (as manufactured) has always been SQUARE, and with some effort it will cram into the opening on both the R and EX. But, after being used for a couple of years, my collars have COMPRESSED and NOW HAVE A TAPER to them. This makes them look like they were manufactured this way, but this is something that happened over time, from the pressure of the metal band that holds the filter in place.

The lesson UNI users need to take home from my experience is that you need to FREQUENTALY INSPECT THE COLLARS ON YOUR INSERTS, and if they are getting squased you need to replace them! If the catalog numbers had not been wrong, I might have reached this conclusion immediately, and saved you all this long diatribe (I was just thinking out loud, and unfortunately shared it all with you)! This all works out well for UNI in the end, because this way they will sell even more filters.