Poking holes in airbox???

10 replies to this topic

Posted July 22, 2004 - 07:56 PM


Would cutting or drilling holes in my 426's airbox improve airflow and as such response? Are there any reasons why this would be a bad idea? Any help appreciated. :thumbsup:

  • nzer

Posted July 22, 2004 - 08:24 PM


yes and yes.your filter will get dirty twice as fast with the holes drilled some motard boys do it though there on tarseal were there is no dust

  • John_Lorenz

Posted July 23, 2004 - 04:06 AM


yes it would, but its not advisable for a machine that runs in muddy, dirty watery areas. Motard yes no issues.

You can get 1 inch filter inserts
for some hints

  • grayracer513

Posted July 24, 2004 - 09:24 PM


Air flows into the airbox on a 426 primarily under the rear edge of the seat, through both "hand holes" in the rear number plates and up over the top front edge by the sub frame bolt. Given that either of the hand holes are considerably larger than the carburetor mouth, I don't believe you would gain anything whatsoever by adding more holes to the box for typical dirt bike purposes. Supermoto MAY be different because of the higher speeds involved, and the way that air flows around the rider at speed.

Your airbox was designed to supply air to a racing engine in adequate amounts while minimizing the amount of stuff the filter has to remove, and more importantly, keeping the filter dry. My advice is to leave it alone if you're riding in the dirt.

  • FFRacing79

Posted July 25, 2004 - 07:01 PM


The FFR airbox mod works on the YZs as well as the CRs.

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • XXX_Thumper

Posted July 26, 2004 - 01:01 PM


I bought a set of air box vents for my yz450. Me and my buddy both have these. You cut a 1" hole in the air box and seal them in there. You can put filter oil on the little filters to help out the dust. You will have to clean your filter more often due to more air flow and will have to be a little more careful when powerwashing. These things add immediate throttle response. You WILL have to rejet becasue of them. I give them a thumbs Up. :thumbsup: :devil:
WB Air Box Vents..................Page #2

  • yz426onNOS

Posted July 26, 2004 - 08:22 PM


I use 4 white brothers one's. They work great. I seald them with rtv.

  • John_Lorenz

Posted July 27, 2004 - 03:51 AM


The FFR airbox mod works on the YZs as well as the CRs.

What is the FFR air box Mod :thumbsup:

How is the season going?

  • FFRacing79

Posted July 27, 2004 - 02:26 PM


John, Therapture has posted pics of the mod on here somewhere. I will see if I can find them and link.
The season is going great. We made the main at The Mile...one of 3 450s out of 15 505s. We were running 6th till the red flag and I pulled the bike off because of a breather problem. We finished 11th at the Peoria HotShoe. The national there is coming up in a few weeks and we are hoping for a good finish there as well. I recently have been helping out UltimateEdgeRacing with their program and we have been kicking ass at the Canadian SuperMotard Nationals. I will be doing all the RedBull Series with them.


Posted July 27, 2004 - 08:50 PM


You replied to my airbox/poking holes question. If you do this mod how will you have to rejet? My jetting knowledge blows. Will doing this cause the bike to run lean? Any help is appreciated!!! :thumbsup:

  • XXX_Thumper

Posted July 28, 2004 - 07:25 AM


You will start popping like mad on decel. I move the clip down one position to richen up the 0-1/4 throttle. I think thats right. :thumbsup:

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