how often do you re-oil the Uni even if he is not really dirty . I wonder if the oil evaporate or run off the filter after some period of time ??

 

Use a good foam oil, Amsoil makes one that is super! I have foam filters on all my other quads, I just keep my eyes on them, when they start to get dirty I clean them, after a couple of days in thick dusty conditions, I clean them. If I'm riding in snow, and wet conditions, I just wait until it looks dirty or my next oil change (I change oil twice a year on the quads... March and Aug. But I have a lot of months without dust up here! I wouldn't go on much more then two real dusty rides without changing it!

 

I use Maxima FFT (http://www.maximausa.com/products/filteroils/fft.asp). This stuff is very tacky. No way this will ever "evaporate". Highly recommended!

Don't use their FAB1, because to get it to penetrate the filter deeply enough, takes a huge amount of spray ($$$$).