K&N V.S. Foam

[Jeff_B]

I just bought a 99 WR400. Should I stick with the stock foam filter or switch to a K&N?

I have been running a K&N on my 400ex for 4 years with no problems but I have recently herd some negative things about the ability to filter small particles.

Thanks!

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[DezGuy]

When I talked to Allen Fox (FOX Engine Works) He said a K&N filter is fine till they get really dirty than they will pass dirt. As long as they are cleaned or changed on a regular basis it will work fine. Allen even used a K&N on some of the Baja 1000 bikes.

[Jeff_B]

Thats great! I hate cleaning those foam filters!!

Thanks for the advise!

[DirtDirectoryDan]

I recommend staying with the foam filter. I have used Twin-Air in all my dirt bikes for years and never had a problem. If K&N were the best option why aren't all of the current desert racers or motorcycle copmanies using them, or even promoting them for motorcycles?
K&N good for sand, not so good for dust and silt. I would recommend spending a few more minutes cleaning rather than a few more bucks fixing.

[Kritter]

Foam...K&N are garbage on a dirtbike or quad. Whoever said they dont like to clean their filter...dont.

Personally I rotate 4 foam filters so if I am lazy I dont have to clean it that time. I change the filter every time out which is every week or sometimes twice a week. If you have a hi performance 4 stroke...a clean filter is the only thing that will keep them alive for an extended period of time. I personally dont like my 7k investment breaking down!

[Vtr_Racing]

I have ran the K and N filters for years without any issues. You gotta clean them just like anything else. After every race just like the the oil. Either a new filter or a fresh clean one.

[Ryno]

For bikes, K&N's suck because they don't trap all the smaller particles. I have seen firsthand what this does to reeds, powervalves, etc. Keep the foam filter. Like Kris, I have 3 sets of filters. One on the bike, the other two in ziploc storage bags, cleaned and ready to go, just need oil. Makes life much easier, and they're not gonna break the bank @ $15 ea.

[J_Lothringer]

Always use foam if possible............Foam is a way better filttering agent than gauze, K & Ns dont really start filttering till they get a little dirty, Then they work ok. Test will prove foam is better, Just clean often and make sure it is well oiled.

[rommel]

My vote goes to the K&N filters. Years ago, we took our 250R out to Pismo for testing. After an hour or so, we pulled the foam filter and saw sand inside the airboot. Our theory was that if a foam filter can't even trap a relatively large particle such as sand, how can it possibly stop silt?
We immediately bought 3 K&Ns and sucessfully raced over 5000 miles in Mexico (over several seasons) with those same 3 filters. We checked the airboot after every race and at all filter changes, and NEVER had any contaminants get through the filters. They cost a bit more, but I'll never run anything but a K&N on any toy I ever own!
Just my 2 cents

[Kritter]

next trip home from glamis I will show you what my intake boot looks like....SPOTLESS and I will show you the amount of sand that comes out of the filter. If you dont know how to oil a filter and wring it out...they wont work, but that is user error.I see that all the time becuase people dont want to get dirty or sticky... I used to be a believer in K&N till I had one on my ranger and had to clean throttle body, MAF and injectors monthly so I went back to stock...better gas mileage and intake cleaning were every 3 months. Also if you notice on a lot of desert race cars you see canisters with paper filters...not K&N or Foam and if they do run K&N they change them out at pits cuz they get dirty...or at least we did until we got the canister type.