Cutting the air filter cage screen????

I talked to a buddy of mine about air flow in the blue beasts and he said he cut out the metal screen on the air filter cage. Has anyone else done this and if so what improvements or bad results did you have. It makes sense that it would improve air flow but at the same time the screen is there for a reason isn't it?

do not do it!!!!

if your bike could catch your air-filter on fire

that would be a bad thing..

I have been riding and racing the YZ-F's since they first came out at the end of 97. I have a sponsorship with Stroker and the owner, Larry Roeseler, suggested I run a regular YZ filter cage. I replaced the stock cage and found that throttle response was better. I could not tell if I gained any horsepower because these bikes have so much. I'm not good enough to tell if one or two hp are gained.

My bike has never caught on fire. I must have started the bikes 5,000 times without any problems associated to the filter or filter cage. If I rode tight stuff (enduros or the like) I may put the stock cage back in just to be extra safe. The slow speeds and extra heat would concern me.


That is what I wanted to know. If anyone had actually had their bike catch on fire. Yzernie I think you know MD03 from FPMN anyways he clued me in on this and I'll try it. The coulds could but the guys that have done it haven't told me horrible burnt out stories. I need every tiny advantage.

I've watched a bike burn to the ground after backfiring through the filter (flooded & trying to restart after a crash) - but I still thought the gains might be worth the risk - so I dyno'd a stock YZF cage against my YZ125 cage. No measurable difference whatsoever.

Agreed the risk is small, but for the benfit (err - none) it's just not worth it (IMHO)...

Dont do it yull go blind

There is a big myth over the screen, Honda has non, after market has non.

Some say cut every other one

I say who really knows does any body reall know, I would bet Yamaha knows why they put a screen on it, I suggest keeping it intact, or cut it out, my bike has not cougt fire I removed every other screen.....

Does that make sence I dont know does anyone really know what makes sence, after all the goverment dosnt know, my boss dosnt know, so who really knows


[ July 05, 2002: Message edited by: E.G.O.**** ]


Check your PM's.


It is kind of hard for me to believe that a screen would stop fire. Couldn't the sealing surface of the air filter start on fire? Or the air boot? Fire shoots out of the pipe once and a while, why doesn't the fender catch on fire?

It sounds to me like a percautionary thing, like a spark arrestor. And I have never seen a forrest burn down from a bike.

The only way I could see an air filter start on fire is if you cleaned it with something flamable like gasoline, or oiled it with motor oil.

The screen also adds an amount of reenforcement at keep the filter from being distorted at full throttle. Since the filter is merely foam rubber, it is easily distorted. At full throttle, there is quite a bit of vacuum in the air box that tends to want to suck the filter into the head. The "dome" shape of the filter relies on the edges providing a good seal so that debris is not sucked into the engine resulting in excessive wear. Leaving the screen intact adds a little bit in the way of keeping that seal integrity. Cutting the screen out adds such minisucle air flow increase that the gain is offset by the chance of increased wear due to the possibility of dirty air leaking around the seal. That's my opinion.

Hey, if a guy wants to let his bike be a guinea pig, let 'em. What's the worst thing that could happen? If his bike burns or if the filter starts to get sucked into the boot, a new airbox filter cage is probably only about 30 bucks. It's replaceable. (Don't know about the rest of the bike.)

Please let us know if you now start winning races because you took the screen out. And don't forget to take some pictures and post them to the list if anything "exciting" happens.

The Honda CRF450 now comes with a screened air filter support and a new screened support has been sent to anyone who purchased an early bike without the screen. The note that Honda sent out explained that there was a risk of the filter catching on fire due to a backfire.

over on the honda side someone posted a pic of a charred airfilter, twas a lil crunchy if i may say so myself

Yeah ok, what was I thinking of. I mean what are the chances of a piece of foam catching fire in a highly flammable fuel/air mix... :)

Bottom line is that thumpers without screens backfire all the time & it's very rare that they burst into flames. But if the dyno & the flowbench don't show any real benefit in removing the screen, then why increase the risk?

I want all of you "my bike is going to catch on fire" guys to take a match to your properly cleaned filter and see how easy it is to ignite. In others words, it doesn't.

Then clean that same filter in gas and watch what happens. Get ready for a little BBQ.

Since not all users follow the instructions, a manufacture is bound to build-in some tolerance.


Just so you guru's without the screen know, honda issued a recall on the cages without the screens. Seems some jokers bike burned to the ground while idling on the stand.

I'll pay the guy that can tell the difference between screen and no screen 100 bucks if gets it right 2 twice in a row.

So I'm going to stick to my theory that an air filter cleaned with soap and water of which is properly oiled will not catch on fire.

And I also believe that washing a filter with soap and water never really gets it as clean as when you clean it with an oil-based solvent.

So I wash the filter with solvent, then wash it with soap and water to wash out the solvent. Been doing this for years with a collection of similar screen-less filter systems. Plenty of backfires, but no BBQs.

Now, does removing the screen make a difference?

Perhaps this will help.

For me, performance is about fine-tuning. In this realm, there is a discernable difference between "bolting" an item to your bike, and "fitting" an item to your bike.

Fine-tuning is orchestrating all items to fit and perform together. Sometimes this means adding something, other times it means removing something.

Often, no single mod will make or break a race bike, but the accumulation of many well tuned mods will make a bike feel tight and snappy (just like a good girlfriend).

I don't think I can directly feel the before and after effects of removing the screen, nor do I believe you would see such effects via the dyno. But, I do feel confident that it's part of the system that makes other 426 owners climb off of my bike, wanting to know what I have done that makes it feel the way it does.

It's like having a well bled brake verses one that isn't. They both work, and you'll most likely not lose any spots in the running of a race, but we know how great it feels to have a good positive connection.

And sometimes, some guys get it so right that it can make a winning machine.

So again, determine what your standards are and feel free to think things out.


DaveJ. That was one of the most intelligent posts I've ever read here. Kudos to you.

I agree with DaveJ 100%,

I clean my filter and always have in hot water and dove detergant, I let the filter soak until the Hot water is room temp then I proceed with the cleaning process.

Once all the dirt grime grease is gone I clean it again with warm water and very little dove.

A third rinsing is done in warm watter to get all the soap out of the foam. I let it stand dry for at least 24 hrs or if its a warm / hot day in the sun for a few hrs.

Then I Oil it and let hang for another few hrs.

Never had a fire.

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