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Is Airbox modding necessary?

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Just bought a Yosh Comp Slip On exhaust for my 2006 CRF450X and wondering if it would really be beneficial to modify airbox. I kinda like it stock. It saved me last week while on a trip to Moab, Utah. Long story short... I ended jumping into 3 or 4 ft of water and was able to ride right through it while my friend on a KX 250 did the same thing and completely flooded his bike.

Also, if I don't modify the airbox...what type of jetting should I be running at 5000 ft ASL? Thanks for the help

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That is a very interesting question. Most guys (my self included) did the air box mod at the same time as the re-jet of the carb. As a result there is no way to quantify any performance gain for just the air box mod. My guess is that most of the gain is from the re-jet. To know for sure one would have to put the bike on a dyno, check the hp and torque, then do the mod and re test. One thing I did notice is alot more intake noise with the mod.

Good luck.

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when you buy the jd kit, it has a chart of what kind of jetting to use. also, since you have bought a new exhaust, it is critical that you re-jet because you have made your bike even leaner. i live in the desert and i took off the snorkel only due to the concern of constant dust in my air box. i live at 4000 feet and have modded my exhaust so i use the 170 main and jd red. (btw- i am planning on modding the air box sides despite the dust concerns since i'm using such a large main)

also, see the following JD pics concerning gains in torque and horsepower gains post jd kit (these dyno charts are with the air box mod of course):

CRF450X Dyno Baffle and No Baffle with JD Jet Kit (Torque)

http://www.pbase.com/jdjetting1/image/41174559

Stock Pipe with Baffle, Stock jetting vs JD Jet Kit (HP)

http://www.pbase.com/jdjetting1/image/41174296

Stock Pipe with Baffle, Stock jetting vs JD Jet Kit (Torque)

http://www.pbase.com/jdjetting1/image/41174305

CRF450X Dyno Baffle and No Baffle with JD Jet Kit (HP)

http://www.pbase.com/jdjetting1/image/41174553

hope this helps

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The mod isn't "necessary" unless.... unless you do other modifications to your bike. For example, more air out... you need more air in. Hence a pipe or less restrictive can, your bike benefits from more air in. More air in... you now need to re-jet... etc.etc.

The snow ball effect.

I just built a 450X with minor air box mods. I only cut the sides of the airbox out. Not the top, or the rear. I jetted it, piped it... and it runs like a champ. No need to cut it into swiss cheese if you don't want to.

But you need to understand "WHY" your doing something before you do it. It helps.

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Take a look at a R airbox and you'll understand why your X is weak.

Of course re-jet is mandatory with airbox mods.

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I ended jumping into 3 or 4 ft of water and was able to ride right through it while my friend on a KX 250 did the same thing and completely flooded his bike.

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... I ended jumping into 3 or 4 ft of water and was able to ride right through it while my friend on a KX 250 did the same thing and completely flooded it

That is a good reason to keep the airbox the way it was designed for... offroad riding thru the elements. Like water crossings. I for one do not want to turn my X into a CRF450 motocross bike. On the other hand I am doing a

pipe and JD jetting kit to boost performance . I ride in Fl. mostly. No desert here . Lots of water and mud I would rather not suck up.

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