Got a funky looking red UNI air filter from Amazon for around 20 bucks. I was not expecting any performance gains, however I was pleasantly surprised by the new crispness to the intake, in sound and responsiveness.
I have a EFI bike with an EJK controller. I found that I could add a bit more cruise fuel to richen it all up with the added airflow.
Clearly the stock filter is chocking the already asthmatic little thumper. So if you have already spent thousands on pipes, BB's, headers etc, get a filter.

 

I noticed a big change with my Uni as well. Definitely more snap. Same with the more open KLX300 exhaust, and with the rejet. Not sure which was the most effective.

However, I must also relay that the Uni did absolutely nothing to prevent mucky water sucking into my carb when dropped in 3 feet of water. Emphasis on the word muck. I also pulled an amazing amount of muck into my crankcase and cylinder as well.

If I could do it over again I'd keep the Uni cause I don't think any filter is up to that task. However, I don't think I'd drill the crankcase vent into the airbox. It's not worth it for the (questionable) improvement it provides.

 

If the UNI flows that much better, a carbed KLX would need to be rejetted then?

 

I go back and forth between a pair of Twin Air's and a pair of Uni's. They're both great filters, but I don't detect any performance increase from either...when I had the stock CV carb and now with the TM36 pumper. Are the Uni's that y'all are using the two-piece 2-stage models like I have? My inner Uni is yellow, and the more porous outer is red.

 

Thumper - yes, you need a rejet with the Uni.

TNC - yes, the Uni is a 2 stage inner/outer.

 

In that case, since I got the jetting so perfect and the removal of the carb such a PITA with the KLX, I will hold off on getting the UNI for now.

 

My bike is jetted stage 2 with a header and pipe and I go between the stock filter and a uni and I can tell no difference between the two.

 

I never saw a need to change from the stock filter. Foam is foam...

 

in both my klx and klr the stock foams are the finest thickest best filtering, but lowest flow. The aftermarket filters seem the k and n and the uni in foams flows the most aiir but can pass the most dust if conditions are such.

uni sells bulk foam in many different grades you can buy, graded by color. In some applications they build with some very course material. buyer beware, or informed. Guys on the klr forum beat me up for it, but I won't run a klr uni in the dust.

 

You definitely DO NOT need to rejet because of a filter change. That is ludicrous.