removing airbox

[mg82]

i was thinking of removing my airbox and running a filter cone directly off the carb. probably a k&n.  has anyone done this before? what was the outcome?

[alan]

Not something I would do, Just because I don't like cleaning my filter!

[mg82]

well i would have a filter skin on it and it would be strictly for drag racing.

[FuriouSly]

Airflow is key in producing power,  especially up top.  This might start a debate,  but that is why we are here on the forum.

K&N filters flow more air than oem stock paper filters in cars and the like, yes.  Yes they can scrub the air down to microns like a hepa filter also.  But they don't flow as much air as a quality foam filter in bikes.  Let the rangling begin!!

If you are going to put a K&N pod on your KX,  its going to be pretty small and have a very small surface area compared to the airbox foam filter.  But if you keep it super clean and oiled in specs (very lightly),  it can work good.

Foam filters need to have a protective airbox and some structure to help keep them in operation.  K&N's have a large gathering in applications where looks and not having to custom fabricate an airbox is more important.

Some thoughts from an insomniac    ..... Sly

[mg82]

i haven't taken the airbox out yet to get a good look at it but i would put the biggest filter that i could fit. i don't like dealing with the foam filters and i think that if done correctly it would be way less maintenance and could very possibly perform way better. i know i have seen some drag bikes runnin it like that as well.

[CAduner]

I agree with sly about the quality of the air that is filtered through a foam air filter compared to a K&N.  I used to have a 87' 250r that I removed the airbox on and ran a K&N.  I noticed a huge increase in power on top, but I think that is due to the volume of air entering the carb.  However I did notice that there was a small trace amount of very very very fine dust in the boot that connects the airbox to the carb.  If I were to ride anywhere but the sand I would never run a bike without a airbox, I dont think the gain in power is justified due to extra work needed to clean the bike.

[alan]

We may want to make this a "Sticky" and maybe rename it "Airflow & Filters", anyway just a thought!

I do agree it depends on where you ride, if you are riding in the dunes or where you are in a lot of water, I would never run without an airbox.

I guess I settled on Twin air filters, not to sure why, but I never see any fine crap inside when I remove it for cleaning.

In my 700 V Force Quad I run K&N with skins. The filter is such a pain in the ass to change it is just easer to change out the skin.

Alan

[FuriouSly]

CADuner

I noticed a huge increase in power on top

are you saying that the K&N gave more air flow for you up top?

However I did notice that there was a small trace amount of very very very fine dust in the boot that connects the airbox to the carb

you had fine dust with a properly oiled K&N?

I dont think the gain in power is justified due to extra work needed to clean the bike.

extra work cleaning the filter?

I think a K&N has its place, just not in a dirt bike.  I have seen a K&N for a KX500 I am pretty sure,  it fits in the airbox and replaces the foam filter in the exact size and space.  Anyone used one before like this??

just wondering about these commments...  Sly

[mg82]

i gonna get it apart and see what i can come up with.

[KXcam22]

The airbox does a lot of directing of air into the carb, but at the expense of ultimate max airflow.  Generally replacing the airbox with a clampon filter will sacrifice power below 1/2 throttle (when the carb air velocity is low there is more turbulence at the carb mouth than the carb intake can fully overcome) but then gain power above this due to outright increased airflow.  I did this to my roadracer and the effect was apparent (and I was looking for top end).  For top end specific type racing this is usually a good mod.  I would suggest building a velocity stack with a filter on it to further enhance the air flow. As to filter types, I still prefer foam but I have K&N's on all my vehicles.  I have heard of the fine dust rumour but don't know if I believe it. It would be nice to talk to someong who races dune buggies in the dez.  He would know for sure if fine stuff gets through. Let the debate rage! Cam.

PS. I once read a tech article that showed how airbox resonance combated turbulence and increased airflow at certain RPM's. Quite fascinating.

PSS.  Who wants to try the first KX500 ram air box??

[mg82]

i got some 1 3/4" I.D. gates straight radiator hose that i'm gonna use between the carb and the filter. probably need some sort of flange from hose to filter to make a f\m union.i might tear into it tonight and see what i can come up with as far as how big of a filter i can cram in there. i am gonna tear the whole motor down so i won't be able to test just yet but i will get an idea an let you guys know

[mg82]

took a look at it tonight and got it all apart. i would have to find something that would make that bend around the shock and stuff the filter up under the seat. also have to make a bracket for the mud flap.

[hillclimber147]

I used UNI Filter pods on my Ducati. They are foam material like filters on dirt bikes, I've been meaning to try these out on my KX 500 hillclimber.

[FuriouSly]

I used UNI Filter pods on my Ducati...hillclimber147

Definately, I like those also.  They have some smaller ones but the bigger ones like in the pictures have more surface area and would last a bit longer between cleanings.  Did those have a mesh cage inside to keep them from caving in under air velocity load?

I would suggest building a velocity stack with a filter on it to further enhance the air flow...KXcam22

A must also.  Most quad airbox removal conversions will put a steel/aluminum velocity tube from the carb up under the seat to the cone filter to help remove the air turbulance at the mouth of the carb.  Good call Cam.

Sly

[hillclimber147]

Definately, I like those also.  They have some smaller ones but the bigger ones like in the pictures have more surface area and would last a bit longer between cleanings.  Did those have a mesh cage inside to keep them from caving in under air velocity load?

They do come with a spring like cage.