Dust Past Air Filter

[Slapnut]

Hi Guys,

I've done a search on this and have'nt really come up with much.

Since new (an '04 YZF 250) my bike has always had dust inside the air boot when I go to change out the filter. My dealer told me that they always find dust in the air boot when they change out filters on the bikes that come in the shop.

I have tried every type of filter oil that I can find, without much improvement.

I have tried nearly every brand of filter as well without any improvement.

I have removed the filter housing from the air boot and applied heaps of silicone to the joint and yet I still have what I would call an unacceptable amount of dust entering the carby.

I know the cage is sitting square with about a 2mm gap between the cage and housing as I've checked this with out the filter.

I've tried squeezing the crap out of the filters to remove excess filter oil and I've damn near not squeezed them at all (with the filter oil running out the bottom of the air box onto the swingarm.

So now what do I do guys?

All the bikes I have ever owned have never had anything like this problem, they all had squeaky clean air boots after the dustiest of rides.

I have post a pic of the problem if anyone else can help me here, and to let me know if theirs are the same as mine or no where near as bad.

Cheeers and thanks

Keith

[vorra65]

Do a search for air filter grease, there was a thread recently that had about a 50/50 response to those that use a bead of grease on the air filter -where it mates up to the intake boot.

I myself, have done the grease thing for 36 yr. Some say it's not needed-I say it's cheap insurance. ?

[Slapnut]

Yeh, tried that too, normal grease, waterproof grease and special air filter top dollar rim grease with no luck.

Does anyone elses look like this?

[Dano426]

Does anyone elses look like this?

No, mine is always clean.

When you are installing the filter and cage, does it fit on there snug?

Do you tighten the wing nut all the way down tight? I am guessing you do.

I am wondering if the dealer messed up and some how swopped the filter cage with a different bike that they were assembling at the same time. I have seen gas caps off of street bikes get put on the wrong bikes??? Just a thought?

[av]

Have you tried adding filter skins?

[YZ250F_Rider]

Check that the boot isnt torn where it clamps onto the cage support. You can see the boots clamp in the pic at 1 o'clock. I silicone our boots to the cage support before clamping them.

You never said how long you go before changing the filter.

[grayracer513]

You never said how long you go before changing the filter.

I was going to ask that. Remember that foam filters work by have the dirt get stuck on the oil film in the foam as it wiggles its way through the filter. Once there is a layer of dust covering the oil on the outside, the dust works its way deeper into the foam before getting stuck. Eventually, you use up all the available oily surface area, and the dust gets all the way in.

Oil up a fresh filter and run it for one ride only. Then check the air boot. If it's clean, you've found your problem.

[tranqwhl]

check this out:

http://www.westsideridaz.com/days/2006-03-01/dscf00500db.jpg

where I put the yellow circle, I file that down. That pushes the filter against the air box even tighter. There was an article in some magazine a while ago talking about this, but I can't remember where I saw it.

[dightonford]

I have always used a waterproof grease on the rim of the filter (lately BELRAY) and i have never seen dust in my boot. I go two rides between cleanings but I trail ride mostly now, so not alot of dust. Just alot of rocks....

We squeeze the air filter oil out, then wrap the filter in a paper towel and squeeze again. Never once had a problem in 20+ years of riding.

[PoorLilRich]

I have always used a waterproof grease on the rim of the filter (lately BELRAY) and i have never seen dust in my boot. I go two rides between cleanings but I trail ride mostly now, so not alot of dust. Just alot of rocks....

We squeeze the air filter oil out, then wrap the filter in a paper towel and squeeze again. Never once had a problem in 20+ years of riding.

jsut curious...but do you ever get a drip of grease down into the boot?

[yamaha259]

It seems that some does escape, I find it is not 100% sealed. I have used grease as well. Although yours looks a bit more fine dust, what type of oil do you use? I use no toil and it is good, but you have to let it dry first, or it drips out the bottom.

[David37]

I have never found any dust or dirt on the inside of my air filter housing. I would try a new plastic air filter cage or maybe one of the Twin Air metal air filter cage, like the one they make for the CR250F, not sure if they make one for the YZ250F. I use No Toil air filter and rim grease and have had good luck. Let us know if you find the source of your dust/dirt.

[Slapnut]

Thanks Guys, I've read the replies and the response has been great and much appreciated but: My son races this bike every second Sunday at MX and I never let the bike go more than one race meeting on the same filter. Even after a half hour play ride the filter gets changed. The air boot definitely does not have a hole or tear in it. I use waterproof grease on the rim face but I have not filed the boss down to get the cage closer to the housing.

We are talking about a climate here in the middle of the Aussie desert where we get about 200mm of rain a year so unless your in front of the other guys, your going to eat dust and were talking big mobs of it (this is where they hold the Finke Desert Race).

I've always been lead to believe that you couldn't squeeze too much oil out of the filter but maybe that where I've been going wrong, I squeeze the crap out of it (so as not to restrict the air flow too much) and then blend whats left over into the filter. What do you guys do when you oil up a filter, I have just now oiled up a filter and have only mildly squeezed it to see what happens this weekend.

The dust you see in the photo is from a one hour play ride down the Finke Track with some mates.

Any more suggestions would be very much appreciated.

Cheers

Keith

[dightonford]

jsut curious...but do you ever get a drip of grease down into the boot?

Never had that problem, and i put a liberal amount on the rim and around the hole in the filter for the bolt.

[RMZrider397]

Use greese like the other posts have said. it works really well.

[goguy]

Lightly grease inside of boot for added protection. Dust will cling, not get sucked into engine.

[bigred455]

I oil the filter from a dishwashing bottle and a pair of disposable gloves. Their is no need to dunk the filter and squeeze.Just squirt on your favorite foam filter oil(dishwashing bottle) I like palmolive and massage in evenly throughout filter. No waste at all!!!! Go around the junction of the airboot and rim with the lights out with a tiny flashlight go around the whole rim from the inside and see if you do have a good seal,just double check yourself.

[Birdy426]

You might try a Twin Air PowerFlo kit. The frame is machined from billet aluminum, and, in addition to looking trick, is a lot more rigid than the stock cage. Might seal better than the stocker...

[MJC476]

I have had a very fine film of dust in the air boot from time to time but nothing like your problem. I have tried different oils I try to stay with the thicker types rather than the new super thin ones. I also don't like to squeeze too much oil out of the filter and put a good smear of Bel Ray on the rim as well as the bolt washer (yours isn't missing is it?) I have an o4 & my local track is hardpack & often very dry & dusty with that good Aussie bulldust.

[Fmx_Aus]

I ride a 04 aswell bud, i used to have the same problem when i was running a 02 Rush filter for FMX just so it would suck the air nice when i was on it hard out for short run-ups on 70-90 foot gaps.

I started using a 2 stage uni filter and didnt have any dust in there at all, and i ride some dusty natural terrain hits now.

cheers bud