Better breathing can give a performance gain, particularly with a muffler change and rejet... but it's at the cost of slightly less filtering... (a drop-in stock filter replacement will do better than an external cone for both performance and filtering - more surface area)...
... but, the main advantage that I have one for, is that they are washable.   Filters are expensive...

Damage from reduced filtering is debatable... many bikes go 100k+ miles with them... maybe they would go a percentage further with a paper filter, or not,...
... but, most bikes die of neglect.... or if ridden, they die from oil pressure failure, catastrophic failure,  or metal fatigue....
JMHO...

justin_o_guy2 wrote on 05/30/13 at 07:22:07:


Yep....That is good advice to keep the original one.  My Trials bike has a foam filter and I have 2 of them.  One is in the bike and being used....while the other one is getting cleaned.  

Firstly,...the box filter has more filter area... if you're worried about the size of the box being restrictive, think about the surface area of the filter...
Secondly,... in open atmosphere, it would in theory have more air, if it needed it... but, there is turbulence out there... even your pants flapping is creating eddys of high and low pressure at the cone...  an airbox is there to steady that air as it enters the filter and engine.... giving a more consistent air pressure to draw the fuel...

Cones are pretty,... velocity stacks are even prettier...
... and full open does do good for a 10 second firebreathing dragster, that will only be running WFO...
... but there aren't a lot of 30hp 650 thumpers in that crowd...

I'm not anti cone or velocity stack,... but they aren't a performance mod... they are a choice that involves trade-offs...
Cosmetic, performance, weight, purpose...
You will get the higher dyno reading,.. in a building, on a tester,(the building is acting as a giant airbox) ... but, you'll lose once you are outside and moving through the wind...