dirt getting past filter

I have an 03 WR 450 and it has been sucking dirt passed the filter some where. There is a thin layer of dust in the boot between the air filter and the carb after dusty conditions such as a desert race, but also sometimes just trail riding.

I have tried everything I could think of.

-First I was told not to use no toil. I tried maxima fft and there was no difference. Same thin layer of dust on boot passed filter.

- I have had three different filters, No Toil, Uni, and stock Yamaha.

- Next I was told I was not greasing the filter rim enough. I put about an 1/8 Inch layer of grease on the filter rim and I got the same thin layer of dust.

- I have also never seen any signs of dirt on the inside of the filter. I would think if it was coming through the filter oil I would se it on the inside of the filter.

- I have taken apart the air box three times now and sealed the spots where I thought it could be coming through with Yamabond. It sure seems sealed tight to me, but dirt is still coming through some where.

If anyone has seen this happening and/or just has any ideas please reply.

Thank you very much


I have photos , but was not sure how to upload.

TT member "EGO" has the same problem on his YZ450 and it is the seal on the outside of the boot that is leaking in dirt. Your filter is doing its job! You have to take the air box out and reseal the boot to the airbox. EGO has instructions on one of his posts where he is rebuilding the bike from scratch. PM him he is a good guy and a great TT member. Take note that we should all check down our boots whenever we have a filter change to look for signs of this seal failing. :)

It is very unlikely for dirt to get through an air filter, but very easy for dirt to get around it. A bit of grease on the inside of the carby boot may also help to trap some of the dirt that makes it through and prevent it from entering your engine.


Yeah, a real fine talc-like dust on the inside of the boot. I've been having the same problem. I was using No-Toil when I first got the bike. Then bought a Twin-Air and switched to Belray filter oil. I've disassembled the air box twice, and both times the sealing areas (boot/airbox, boot/carb)) were perfectly clean. The last time(couple weeks ago) I put a bead of Permatex on the seal when reassembling. I did a desert race in New Mexico last week but haven't looked behind the filter yet. I'll try to get to it this weekend and let you know. At this point though, I think the dust is passing through the filter(with some filter oil,since it seams to be slightly tacky), because all the sealing surfaces on the boot have been clean. :)

I know this is a silly question, but in the name of trying to help I will ask anyway. You are sure you are oiling the correct filter right? The inner one, and not the outter?

Just trying to help resolve it. :)

I have used only the factory filter and TwinAir. From my experience, the factory is much better.

In extreme dusty conditions, I have had dust get past the Twinair. On the same trails on the same day/weekend, the factory filter didn't have the problem. Makes sense, too, since the factory filter is bigger and thicker.

IMO, the extra airflow that the aftermarket filters claim is not worth any potential increased wear on the engine. If I were racing, I may feel different.

just my x2 cents

Indy, I must have missed the same boat Cowboy did on that thread. I don't see what item(s) 10 on that fiche have to do with dirt getting past the filter. This airbox looks a little different than (I remember)my 450's, but items 11,12,and 13, along with the main box(10) form the seal I've been concerned with. It just seems to me(I could be wrong)that the same coating of dust that is inside the air boot would also coat any route it might be taking past the seal.

Bagwell- my filters "inner" and "outer" are bonded, so it is impossible to oil one without the other.


At least you get to Ski Lipskid! :D We get snow & ice here in Indiana and you cant do anything, no snowmobiling, no real skiing, no fun riding! But I was out today in 50 degree weather and bright sunshine! Had a blast with some real good jumping kids. Can you imagine 140 ft natural terrain table top pinned in 4th gear! It was fun watching the 21 year old out jump the 18 year old brother. I am older then both of them combined. :D They wore me out all day. :D

Anyway I think the seal behind the filter to the airbox can leak over time and we should check for signs in the air box boot.

I think good oil and any filter will keep the boot from getting a dust & dirt froming on the inside. :)

I would go to a UNI two part filter. I have never had any problems with them and never noticed any dust inside the boot. I use BelRay filter oil and it works great.

Good luck finding the problem.


I coat the inside of the boot also with a very thin coat of grease to catch any dirt that may pass through the filter not much at all. I have herd that this is a common problem with Yamahas but most people probally are not checking or just dont care.

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