09 yz450 airbox question.

I was told by a friend that the screen in the air filter cage needs to be removed. Do you guys notice a difference?

a fraction of a horsepower you would never ever notice and you risk catching the bike on fire. You tell me if its worth it.

No one I am aware of has ever documented any gain from removing the screen. Doug Henry's crew spent a lot of time on the air box setup of his '03 (?) bike and concluded it was a waste of time to bother with it at all.

It doesn't "need" to be removed, and there may be no measurable gain in horsepower, but removing it provides for crisper off idle throttle response.

It is noticeable on initial power application (out of corners for example) if you are a moto purist. :smirk:

A YZ250 filter cage is a direct replacement without the screen.

It is noticeable on initial power application (out of corners for example) if you are a moto purist.

I'm a "moto purist", and my experience is that there is nothing to it. But if anyone wants to spend $25 to find out, go ahead.

I would not advise simply cutting the screen out of your existing cage. Doing so runs the slight risk of having loose bits of stainless wire fall free into the intake.

its a joke, there can only be so much pulled through the intake and the screen will let far more air through than the filter will.

I would not advise simply cutting the screen out of your existing cage. Doing so runs the slight risk of having loose bits of stainless wire fall free into the intake.

Not to mention being poked everytime you wrap your finger around the cage where the screen once was.

as funny as it may sound but in my line of work screens always go. dont quote be but I believe screens create a 30% loss of are movement. Whenever we are venting a home, the screen always goes and it make a big difference. Stick a fan in your window at home with a screen in and then without, substantial difference. Anyhow, I dont know at all if this translates at all to the airfilter. I dont want to say one way or another, I just know an actual place it does.

The analogy doesn't work because the windows of which you speak don't have a dome of oiled foam over them. If the air filter were not there, then removing the screen could potentially increase air flow at full throttle. But the fact is that the filter is more restrictive than the screen, so removing the screen does nothing.

The analogy doesn't work because the windows of which you speak don't have a dome of oiled foam over them. If the air filter were not there, then removing the screen could potentially increase air flow at full throttle. But the fact is that the filter is more restrictive than the screen, so removing the screen does nothing.

Perfect logic gray, I'm with you on that. I didnt think of it that way.

It's not really about flow rate per se. It's about accelleration of the intial charge of air from the airbox.

It's about getting a slightly cleaner and more voluminous pocket or slug of air just at initial throttle opening. That's all.

Obviously most people can't feel it or don't give a shit. I'm not one of them.

The intake boot shape on modern four strokes is as highly engineered as the exhaust pipe shape. Small changes in shape and volume make a big difference in the feel of the motor. Not necessarily horsepower but "feel".

With the screen removed the initial charge (between the screen and the filter)doesn't have to accellerate through the screen, the effect is a slightly denser air charge and quicker response.

No big deal. It's not going to lose you a race, and a race team should probably leave the screen in for liability purposes. It wouldn't look too good for their sponsors if their bike burned up...

I've never had a problem with my bike burning up...Yet. I guess if it does then it's obviously time for a new bike.:smirk:

With the screen removed the initial charge (between the screen and the filter)doesn't have to accellerate through the screen, the effect is a slightly denser air charge and quicker response.

That's a good theory, except that the relatively still air between the filter and carb can't be accelerated with or without the screen until air flows through the filter to replace it.

Magic Feather.

That's a good theory, except that the relatively still air between the filter and carb can't be accelerated with or without the screen until air flows through the filter to replace it.

Magic Feather.

Sure it could. But then you'd have a vacuum. Thus a dead motor that even a magic feather couldn't fix. And lousy throttle response.

So removing the screen fundamentally changes nothing.

So removing the screen fundamentally changes nothing.

No. It changes something.

ok ok ok, i found this sticker once that i put on my bike and it made me go so much faster!

If you do want to eliminate the screen,id go with a loud mouth air filter kit;or a pro design kit.They come with a billet housing that attaches to the air box.So all that is required when changing/replacing the filter is a 8mm socket.I run the pro design kit on my yz450f and my yfz450 its the cats a$$.

Thanks for the replies. I did not think it would affect it much if any. The power the bike makes it great for the woods. Now if I could keep it from stalling in the tight stuff it would be perfect.

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