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Discussion Starter · #1 ·
I've heard that modifying (or removing) and airbox can yield a 5% increase in power and a much nicer, stronger sound.
+, it's 'illegal' in most places, which is always fun. :p
I've heard of some people saying that this will allow the filter to get wet...
Has anyone on here done it? What are your results?

When I install a k&n filter, I plan to do one of the following;


-Remove airbox cover only
- Remove cover and gut out box snorkel, baffles, etc
- Remove entire cover and box
- Re jet accordingly

Any thoughts on the subject of airbox mods?
 

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Discussion Starter · #3 ·
If you run in a flooded zone or really heavy rain, yes, a K&N or pod filter will get wet.
Never ridden in such conditions, so I can't tell if it gets wet or not.
Here's a DIY for this (use the search) :
http://www.kawiforums.com/ninja-250...ir-box-installing-aftermarket-air-filter.html

How it looks in my ninjette:


You need to rejet, use a air/fuel meter or a sniffer to do this at a dyno.

Cheers
Very cool. I usually ride in the rain, so i didn't remove the whole box.
I did however add k&n filter, remove snorkel and leave cover off. Sounds like a beast!! :D
 

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The rain isn't too much or an issue. It's in a spot that is pretty well protected from the elements. That said:

Pros - More airflow at higher RPMs. This entails more horsepower.
Better throttle response.
A lot more space

Cons - Lack of Helmholtz resonance at lower RPMs means you LOSE power at lower RPMs
Increased intake noise. You can HEAR the engine sucking.
Difficult to remove airbox and reinstall later.

That said: K&N air filters don't do much in most applications and the drop-in air filter for the 250's don't do anything for horsepower. Some people started drilling holes in their airbox or riding around with the inspection cover off :rolleyes:. Drilling holes in the airbox will allow more air to flow, but permanently ruins your airbox so you can't "undo" it later. Leaving the inspection cover open is just dumb. You're literally allowing air to completely bypass the filter. Sure you're going to get more air through, but it's completely unfiltered.

I think if you're going to fiddle around with this either you do nothing or you completely remove the airbox. Any other method is going to ruin your airbox or ruin your engine.
 

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Discussion Starter · #5 ·
The rain isn't too much or an issue. It's in a spot that is pretty well protected from the elements. That said:

Pros - More airflow at higher RPMs. This entails more horsepower.
Better throttle response.
A lot more space

Cons - Lack of Helmholtz resonance at lower RPMs means you LOSE power at lower RPMs
Increased intake noise. You can HEAR the engine sucking.
Difficult to remove airbox and reinstall later.

That said: K&N air filters don't do much in most applications and the drop-in air filter for the 250's don't do anything for horsepower. Some people started drilling holes in their airbox or riding around with the inspection cover off :rolleyes:. Drilling holes in the airbox will allow more air to flow, but permanently ruins your airbox so you can't "undo" it later. Leaving the inspection cover open is just dumb. You're literally allowing air to completely bypass the filter. Sure you're going to get more air through, but it's completely unfiltered.

I think if you're going to fiddle around with this either you do nothing or you completely remove the airbox. Any other method is going to ruin your airbox or ruin your engine.
Is my method, k&n + no snorkle + no cover acceptable?
Will that ruin the engine?
 

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:squint:

The rain isn't too much or an issue. It's in a spot that is pretty well protected from the elements. That said:

Pros - More airflow at higher RPMs. This entails more horsepower.
Better throttle response.
A lot more space

Cons - Lack of Helmholtz resonance at lower RPMs means you LOSE power at lower RPMs
Increased intake noise. You can HEAR the engine sucking.
Difficult to remove airbox and reinstall later.

That said: K&N air filters don't do much in most applications and the drop-in air filter for the 250's don't do anything for horsepower. Some people started drilling holes in their airbox or riding around with the inspection cover off :rolleyes:. Drilling holes in the airbox will allow more air to flow, but permanently ruins your airbox so you can't "undo" it later. Leaving the inspection cover open is just dumb. You're literally allowing air to completely bypass the filter. Sure you're going to get more air through, but it's completely unfiltered.

I think if you're going to fiddle around with this either you do nothing or you completely remove the airbox. Any other method is going to ruin your airbox or ruin your engine.
Here's a picture from Kkim's thread about removing the snorkel. Here's the removing the airfilter step:

The grey foam thing is the airfilter. With the inspection cover open air is able to completely go around the filter through a gap similar in size to the hole that air flows INTO the air filter housing normally. So you double the amount of air entering the air box essentially and over half of which is unfiltered... That's the part that is bad news bears for an engine.

So no snorkel + K&N drop-in filter is acceptable. Leaving the cover open is not advised. And as I've said a many times a drop-in K&N filter for the 250's is basically just a waste of $50. BASICALLY if you're going to leave the air filter box in place just remove the snorkel, shim the needles, and call it a day.
 

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Discussion Starter · #7 ·
Ah, I see. But, if unfiltered air is bad for the engine... then removing the whole air box seems incredibly stupid, because 90% of the air would be unfiltered...
 

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No, you remove the airbox and add:


Another air filter. You get 100% of your air filtered just like stock, but no longer have a small port and/or snorkel to pull all of that air through.
 

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Discussion Starter · #9 · (Edited)
No, you remove the airbox and add:


Another air filter. You get 100% of your air filtered just like stock, but no longer have a small port and/or snorkel to pull all of that air through.
Ah, I see. That looks awesome, VeX! Where did you get that filter?
Your bike must be pretty loud, running a downpipe and this mod.
 

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That's the difference. Some people run dual air filters. A couple of years ago I measured the distance between the two carbs and the diameter of the inlet and found the K&N R-0990 filter was a perfect match. This is all mentioned here: http://www.kawiforums.com/ninja-250r/115443-removing-factory-air-box-installing-aftermarket-air-filter.html

That's if you REMOVE the airbox. From what you listed from K&N's site the '08+ filters are drop-in filters. Those literally replace the factory filter. They are worthless unless you drill holes in your airfilter box. So if you're going to leave the airbox in, just leave the stock filter. It's just as good as the K&N and is serviceable just like the K&N. They don't list the dual filter one there because it's not a direct replacement! If you remove your airbox though K&N P/N R-0990 is the filter. There are single pods so you can put a separate air filter on each carburetor, but I never bothered looking them up because the R-0990 works fine.
 
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