hi ,my friend have 2001 ds650 with factory air filter . we used this quad without oil the filter , is this air filter need oil ,or its should be dry ? thanks .

 

I think you would not want oil on the factory paper filter. It would gum up with dirt and crap very quickly with oil. Make the investment for a K&N, Uni, or NoToil... they will last much longer. The factory paper is not really washable, and reusable.

 

the original metal/paper filter is cover by foam filter ,non of them need oil ? thanks

 

Yes the no-toil, K&N and the uni all need oiled. Just not the stocker. Switching to an after market filter will gain you some hp also.