I have both, but only use the orange ''screen type''. the foam one you use with oil and then put the orange one on top. It's for extreme conditions...something like in the ISDE. Too much for every day rides.
The paper I'm referring to studied foam filters only. But you're right about the gauze K&N's... I've seen countless articles and engineering papers condemning oiled-gauze filters for use in anything except frequently re-built race engines. The particle passage data on K&N "filters" is sobering when compared to conventional filters.
In 1980, Kawasaki made a KDX 250 that came from the factory with a Don Vesco gas tank and a K&N filter. I thought that I was being careful when I washed the one in mine, and letting it dry all the way before applying the special K&N filter oil to every fold in it. But I soon found that a lot of fine dust was making it's way through. I held it up to the light and could see specks of daylight through it. That's when I bought a Uni for it.
I do the prefilter [skins] techniqe also only I use up all 3 prefilters, then my filter regular filter before washing. Which reminds me of a time when I bought a 86 KDX200 really cheap because the owner couldn't start or keep the bike running. I bought it thinking of a possible top end job but found the air filter oiled to the max! It couldn't breath! Purred like a kitten after that.
i clean my filter every ride maybe a bit over the top but its better than a topend re build i have 4 twin air filters and use them all when dirty clean them all togeather that way its not as mutch as a problem cleaning
I've seen people change thier air filter every ride, my theory is you have more of a chance to get crap in the motor during a change than with a slightly dirty filter. I dont think anything really gets through a dirty filter, it just starts to reduce air flow. I've gone maybe too long between cleanings but have never seen the inside dirty.
