Where did the current airbox design come from?  Every bike I've owned since my 1982 IT465 has had a foam filter on a plastic cage, with a long wingnut going through the centre to suck it up against the airbox.  I've never given it a second thought, until today I stumbled across the loudmouth intake, which is a horribly over priced piece, from a company that makes seemingly baseless claims.  None the less, it made me question:

Why don't the OEMs use a slip over rubber sleeve and hose clamp to mount the filter?  It would provide much more uniform clamping force on the sealing surface, and eliminate the foam-airbox sticking/grease/neoprene/leaking dilemma.

Any thoughts?

I have the loudmouth on my bike and it has noticeably more bottom end. The best part is the hose clamp. There is no cage. And on the modern 4 strokes there is a screen and the loudmouth gets rid of it. And all the loudmouth filters fit every bike with a loudmouth intake so there is no buying it machine specific.

I'm not so much interested in the loudmouth, I'm curious why the OEM air filters, and the other aftermarket ones, use the wing nut design vs the hose clamp?

The hose clamp holding the filter on a stub flange of some sort is far from a new idea.  Pretty much all of the first Uni foam filters went on that way back in the early '70's.  IMO, it's not as good a system as the current bolt through the center design.  The current design used by Yamaha YZ's (other than the EFI 450's) has more sealing area between the element and the flange than the loudmouth does, for one thing, and the center bolt is less prone to dropping the filter entirely off the flange if it loosens slightly.  My only objection to it is the lack of an internal sealing washer around the bolt hole to help seal it at that point, but I've never seen any evidence to suggest mine has ever leaked there.

The absence of the flash screen does nothing for the engine at all, at least on YZ's, as it is less restrictive than the element itself and the protection against the very real risk of a fire is worth keeping it.  Doug Henry's SM team mechanics did several dyno tests of a lot of different air box configurations and ended up leaving it almost completely stock, including the screen.  They found no benefit in removing it.

I never grease the sealing flange.  If you use a good enough filter oil, that will seal the flange perfectly well.

One of the interesting aspects of the claims made by Loudmouth is that one of the places most likely to fail to seal on a CRF is the big "hose clamp" that secures the air boot to the filter flange.  Food for thought.

Thanks gray,

I have reeds instead of a screen, but the sealing area was the part I was wondering I guess...  Out of curiosity what oil do you use, that stays tacky but doesn't glue itself to the airbox?  Do you run a neoprene gasket?  I've never seen scoring or had bearing trouble, but I do know some fines are getting past, because I've seen some stuck to the cage from time to time on the dustiest days.

I use Maxima FFT.  It will stay tacky for weeks on end, longer if you oil a filter and bag it after it airs out for a day.  It's very tenacious, but will make a mess if you slop it around on stuff.  I put the oiled filter, screen and mounting bolt together in a plastic grocery bag so I can get it into the air box without rubbing oil on the frame rails or dirt on the element, then peel the bag out once the filter's in position.

Nothing 100% stops all of the very finest dust you'll run into, unfortunately, and some gets past the very best filtration.   if you really want to know how well your filter is working, remove the top of your FCR carb.  There's only one way for the dust you see in there to get there.

the  vents on  the  FCR  carbs  are not one way,  if  you  really  want  to help prevent   wear  and  git in the  motor, invest in a  vent filter  from  uptite, works like a  charm,  run one  and  take it apart  and clean it,  you  will see how much  ultra fine silt  gets in  the carb...    run  them on all my  bikes. cheap insurance... IMHO