WR air box modification

Has anyone done any airbox mods for the 03' WR? Since the battery area has inherited about half of the airbox, it would make sense to open it as much as possible. The 450 guys have claims of more HP buy removing excess plastic around the snorkel area and the top of the box.

I just took the snorkle out.

Just drill out the two rivets that hold the bracket for the battery strap and pull the snorkle out, then re-rivet the bracket or whatever its called.

I read that post on the 4xx side, my take is it's best to relocate the battery then open up the air box - why do you think Yamaha put a wall between the battery and the air box? It is unlikely, but a bad backfire and the battery may not go well together if the wall is gone... :) Someone wrote a while back on the 4xx side about a backfire lighting up his seat and eventually his whole older model bike (he may have had his air filter screen removed but you can see that a bad backfire can be pretty fatal). Having a battery/bomb under you exposed to this kind of fire when such a backfire happens is not ideal :D :D I have had my air filter charred to a brown color on the inside without realizing that I had any backfire going on and I have my screen in place! If you are to do the mod suggested on the 4xx side, make sure to keep your air box screen in place and hope for the best when you ride... :D

I definatly think it is a mistake to compromise the battery box and expose the battery to the intake. Removing the air filter screen is asking for a fire! What about removing the excess area where the snorkel was (in the bottom of the box and the backside near the fender?

I don't know about you, but when I ride, I get dirt/mud/goop stuck ALL around my air box, so I don't want ANY side of my air box exposed to the elements, you might get that stuff stuck on your air filter if those places are cut away and that wouldn't be good. Do some riding in really muddy/wet conditions and see how dirty your bike gets, if things look fine around the air box then do the mods in the dry areas (I bet you won't find any). If you ONLY ride on dry tracks, then you'll probably be OK with cutting some of the air box away - I'm too scared to be exposing any side of my air box to the elements, I've seen too much junk stuck on the air box in bad conditions - there is no way for me to be doing that to MY bike...

I think that you may be OK to remove a little of the rear of the air box above the fender. It is really protected there. The only mud and crud that get in there have to either get through the cracks or the handle holes in the side panels.

It really isn't much different than having the top of the airbox open.

I'm still leaving my air box as is since it doesn't come with the baffle. :D I'm guessing that this is more of an issue filling a 450 with air than it is filling a 250 with air.

A quick test with the side cover off the airbox will confirm just how large the issue is on the 250 bike. :D I believe that this will also be very dependant on the exhaust system on the bike. My stock silencer has a 1" opening, and I'm guessing a YZ silencer has a 1 1/2" opening.

I'd do the test immediately but I'm afraid of getting too much snow and ice in my air filter! :D:)

If no one else posts the results to this test, I will once I get my bike outside. Actually, I'll do the test on my own regardless since I think that it depends on other factors like YZ cam timing, exhaust, jetting, rpm, load, elevation, temperature, etc.

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