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Bturner

Air filter screen mod?

19 posts in this topic

I looked around on here to see if there were any threads about removing the screen. I didn't see any, so sorry if this has been talked about before.

My 250x the screen popped right out, but I noticed the 09 is one piece. I hate to buy a twin air power flow kit if I don't have to. Are you guys just cutting the screen out? Then going up 1 on the main &/or raising the clip 1? (I have a full fmf mega /4.1 to)

If there's a thread with this, just post the link. Thanks

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i cut it out and used a dremel to get all the metal off of the plastic to make shure nothing would come loose and become a problem

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I clearly recall that Doug Henry's 2002(?) Super Moto crew did a series of dyno runs testing a variety of air box/intake mods to see what worked and what didn't.  Removing the screen from a highly modified YZ426 SM engine made no measurable difference.  At all.  Same screen they still use.  Flow testing explains that the reason for that simply is that the filter element is more restrictive than the screen is.  The impedance to air flow is the same whether the screen is there or not, so there is nothing at all to be gained by ditching it if you're talking about a '98-'09 model.

 

I have heard that the same is not true of some models or CRF, but YZ/YZF models of those years don't have any really significant faults with their air box design.

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I know of someone who removed the screen , made no difference to power. It made a big difference to reliability though, one day when he changed his filter a stone got past the goal post, found its way into the inlet on a ride . One stuffed valve, cracked piston and some nasty head damage later he wished he had not bothered !

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I know of someone who removed the screen , made no difference to power. It made a big difference to reliability though, one day when he changed his filter a stone got past the goal post, found its way into the inlet on a ride . One stuffed valve, cracked piston and some nasty head damage later he wished he had not bothered !

 

An unintended benefit, but one worth having: secondary filtration. 

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Interesting. It seems just a bit restrictive for air flow. Even on my 2010 250r fi, when you did the air screen mode you had to get the bike remapped or it ran like poo (which was highly recommended), Made all the difference in the world. With the 250x it was just part of the uncorking process, (which was highly recommended), along with cutting the air box & removing the baffle, made all the difference with the proper jetting. Ok, thanks for the heads up!

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Watched a friend of mine pull an air filter at the races one weekend to change it.  When he hauled it out, he started jumping around and making noises like he had a rattlesnake in his hands.  Turns out the seam at the bottom of the filter had opened up, and he was freaking out about what might have gotten into his engine.  The screen had certainly allowed some fine dust through, but it also caught quite a bit, along with some fat grains of sand.   He was glad it was there.

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Yea I don't want a rock or sand going in either, but all my years of riding & all the bikes that didn't have screens in them, I never had this issue. I'm not going to mess with the oem screen, but I may try a twin air power flo cage. I have a discounted sponsorship with them for 14, so I can actually get it for a decent price. Think I'll give it a try.

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The screen on a YZ will not stop things from going in the intake while you are changing filters, as the screen is built into the cage and the cage will be removed when you remove the filter. If you want a cage with no screen, buy one for a YZ125 or YZ250 two stroke, these are the same as the four stroke cages but with no screen. This is way cheaper than the Twin Air Power-Flow kit.

Edited by KJ790
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The screen on a YZ will not stop things from going in the intake while you are changing filters, as the screen is built into the cage and the cage will be removed when you remove the filter. If you want a cage with no screen, buy one for a YZ125 or YZ250 two stroke, these are the same as the four stroke cages but with no screen. This is way cheaper than the Twin Air Power-Flow kit.

I didn't know that. Thanks for the heads up.

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Does it matter what year yz125/250 it is? They all say they fit up to yz250f, but that has the same box & filter as the 450 right?

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Other than the presence of the screen, all YZ/YZF filter elements and cages are interchangeable from '98-'09.  There is, nevertheless, no advantage to removing the screen whatsoever. 

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The only advantage I have found is that it is easier to put the cage in and pull it out of the filter if the screen is not there.

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i cut it out and used a dremel to get all the metal off of the plastic to make shure nothing would come loose and become a problem

I should of added that i felt no difference in performance.

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The screen on a YZ will not stop things from going in the intake while you are changing filters, as the screen is built into the cage and the cage will be removed when you remove the filter. If you want a cage with no screen, buy one for a YZ125 or YZ250 two stroke, these are the same as the four stroke cages but with no screen. This is way cheaper than the Twin Air Power-Flow kit.

This is what I did. Bought a cage for a YZ250 and used a Twin Air " backfire" filter. But I never had a cage to begin with, my bike had a K&N in it when I bought it.

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I know for a fact that a filter cage off a 99 YZ250 two stroke will fit into a 2009 YZ450.  Already done it, it's what I'm running now.  I had the 99 for 12 years until I bought the 450 last year and I had 2 Uni filters for the two stroke.  I didn't want to sell both of them with the bike so I decide to see of they would fit the four stroke.  Low and behold they did so I tried the filter cage to get rid of the wire mesh and low and behold it fit also.  As others have stated I didn't necessarily see any performance gain, but I just didn't want the wire.  I was new to 4 strokes and believed there would be a performance gain with less airflow restrictions, only to find out later after I sold the 2 stroke there wasn't any appreciable gains.  I also added the PC racing neoprene gasket to the cage/airbox interface to help with sealing.  Been using this for the past year and a half with no issues.  But then again I ride MX only.

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