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Discussion Starter #1
I have seen those homemade modifications done to the stock airbox on many 400ex's. Like drilling holes on the lid, or even taking off the lid. I have always wondered, do these mods actually work? Are they even safe for your motor?
 

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yes taken the lid off is safe to do i do it
 

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You have to give the motor more air and fuel to make power.If you just give it fuel it will not open up to the full potential.I would recommend a K&N filter so that it's cleanable.With the opening you'll get some dirt in it.
 

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yah i run open box and go through some deep mud u be fine as long as u clean it
 

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Discussion Starter #5
what about drilling holes in the lid? has that been effective?
 

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i dont know
 

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I have a lid on mine and a K&N air filter. I see no reason to remove the lid. You can jet the carb and steal keep the lid on. If you want to remove the lid I would make some kind of filter to replace it with to keep most of the trash out
 

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Dynojet states for stage 1 jetting you leave the lid on for stage 2 jetting you remove the lid but aftermarket mods are needed eg. exhaust and k&N filter. drilling holes doesn't help much I have 3 lids 1 drilled 1 half cut-out and the last is stock nothing done. I personally run with no lid, but you have to make sure you have the proper set-up.
 

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Really depends on your riding conditions. K&N makes a great product, they will let more dirt through than a foam filter but they also allow more air to go through. If you ride extremely dusty condtions, stick with a foam filter and you are safe running open box. If you want to run a K&N I HIGHLY recommend a pre-filter. For muddy conditions, I would run closed air box. You do NOT want any moisture getting sucked into your machine.
 

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Agree, I clean mine everytime I ride for any length of time.

id stay away from k&n motor killers unless you keep it very clean.
 

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Deffinetally run a pre filter.It'll ketch the littler stuff the filter it's self won't.And I run with the air box lid modded.I cut inbetween the bracing and then only some of it.Probably about 3x3 inch sections.But I tried to let enough meat to keep it strong.
 

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i run a k&n air open box no pre filter and i ride through some deep mud and creeks and mudpit it works just fine with out a pre-filter and i ride in sand to it does just fine without the pre-filter
 

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I clean my K&N after every ride. I have 2 and I carry the extra with me if it is really dirty. I also have a stock airbox. If I was going to mod or something of that nature I would order an Aluminum airbox. It relocates the battery and It is a stronger box and they also have lids for them.
 

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well I'm going to get a foam filter and i might get a pre-filter sooner or later
 
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