125-200cc 2009 WR125 Air Box Mod

About 1/8'' sheet rubber that I have no idea where it came from…

3/16'' alum. rivets with the matching 3/16'' alum. washers. I did not take the box out to do the mod. I needed to slip the tank and side panels on and off. I was able to drill and put the rivets through from the back side. The washers need to be used on the front or the rivets will pull thru the rubber. After I had each piece held in place where I wanted it, I outlined the box on the rubber and also put on a line up mark. Than I removed the side covers and tank to do the work on the marks. At this point the box could be pulled to make access easier, but I did it with the box in place. There are three different pieces…The sides are trimmed to just touch the inside of the side panels and the middle piece overlaps the side pieces and gets bent slightly forward when the gas tank is installed. The rubber is also trimmed to clear the air boot flange, in case it needs to come apart. It took a little time to get the bottoms trimmed right where the panels insert into the 'V', but it can be done... Best part; Nothing is visible when fully dressed.



In these pictures the bike was pressured washed but not really detailed. But I wanted to show the filter 'as is ' after the Ohio GNCC race. Mostly air borne type of collection, nothing splashed on…After the previous race, without the mod, there was about a 1/4'' of muck stacked on top of the filter. This seemed to work at stopping that...




Yes, the top end is pulled…did not look to bad. Going for piston, ring, etc…


And a few head stays...One cracked, one broke...

I'm next, thanx for the advice!

now that is a good idea. way better than tape and foam. good job again mister.

MattR...The carb vent lines? T'd off the lower hoses? Lower hoses still
in place? Looks like my next move...the boy clogged the lines last time out and the carb bogged a little towards the end.

And yes that is a clean filter...and bike!

You guys make my day...

Not the B word again

Maybe they opened up the air box in 09 to help it to breathe

Any other way to get air in to the thing ?
It needs two small air scoops which have mesh or something over them

I think this type of bog was all my doing...there is plenty of space for air to enter and the Mikuni did just fine. This bog was caused by all the carb vent lines hanging below the bike being clogged shut with mud causing the bike to starve a little.

That's why I was asking about the vent lines running in the air box. I had been warned to get this done, but did not. I understand there are a couple of options...

Any suggestions?

I noticed that when i washed my 08 water would get on the air filter... It rides down the tank under the seat then over the top of the rubber flap and onto the filter. I wash with a garden hose btw and don't blast the bike but it still gets down onto the air filter ... not much but it gets there ... so ...maybe run that rubber flap over the gas tank and not under??? it would still provide protection for crap coming from the motor area and would keep and dribbles of the tank from getting on/in filter no?? I'm still running it under the tank at the moment. But for a real wet ride or getting stuck in the rain ...

Yes, if the carb vent hoses get plugged the b word happens. I did the same thing and never got around to doing it.

Take the top 2 and get them up in air box, take the other 2 down normal, someone recommended splitting them up the middle , which is an excellent idea. I usually cut them at a steep incline angle with the incline facing rear of bike. I like the split idea best on bottom ones.

lots of options. i shorten em some, split 'em and coat them w/ PAM, et al. seen one guy use a ventiltaed film canister glued on the case with hoses going into that.

just make sure the hoses gots no bends/loops in them that would allow pooling or drain back of liquids into carb.

I have a 2007 Husqvarna WR250 which has a rubber flap like MattR (see above pic).. Previously when I washed my bike (with regular garden hose) my air
filter was getting some water on it (not a lot but some).. The last time I washed it I removed the seat and placed a plastic bag over the air filter opening
and re-installed the seat.. When I finished washing the bike I removed seat and plastic bag and there was no water on my air filter.. Try it.. Cheers..

thats what i do

Good tip . When in the mood..
I remove the filter and put a plastic cover on from a YZ
you can then clean the inside of the filter box gets so much crap in the bottom there

Or use one made for a Husqvarna.. Twin Air makes one (generic photo below).. Twin Air Part # 160085 (check twin air site for your application)..

Nice job on the air box mod. I've been meaning to do the same on mine, but the original job I did with racer tape doubled up, has held up. The sheet rubber is a much nicer way to go. Make sure you put a filter on the vent hoses you run up to airbox. If you don't, gravity will put dirt into carb and engine. I presently use a 7602 filter, but have used a small Rx pill bottle with the lid drilled and old filter foam.

Wow…new people chiming in! Thanks for the advice…

I have a couple of filters, which I change often so the water on the filter from cleaning does not bother me a whole lot.
(if you're going to clean filters might as well do a couple at a time)

The muck in the air box does…so I think the Twin Air Cover is a good investment.

When the boy washes the bike, it's on the stand, laying on it's sides, seats off, side panels are off…I'm surprised it's not turned upside down…We've been over all the do's and don'ts, he's actually kind of a clean freak…(I think he remembers being told I won't work on a hogged up machine)

I don't know much about the internal chambers of the Mikuni; but do all these hoses vent the same area of the carb? Or are there different circuit's theses hoses serve? Being that the two hoses dive into almost the same place on each side…

Posting pictures of the bike from when it was new…you had us thinking you were the original Mister Clean…

I'm on the new idle screw….what a pain the stock setup is.

Again, Thanks…

I stripped down the '09 when I first got it to grease and do mods. I was suprised at how the airbox was more of an air filter holder, than the airbox on my '02! I thought I saw the '11 bikes get an improved airbox, so will be interested to see what they do.

Thats what I do ...
I'm more concerned about what happens if you get stuck out in the rain or ride some 100 mile turkey run or enduro the day after it has rained 3 inches. Water on my filter from washing is of little concern, dirty muddy water dribbling on it on a regular basis during an all day mud/water ride ...... just saying