Bonneville America Forums Forums Technical Forums Performance Mods air box drilling single unifilter.

I was just wondering if one could drill a hole in the bottom of the air box where the air filter sets, and then drill a corresponding hole in the bottom of the single filter. If this would actually get more air flow with out going entirerly ghetto freak as in master Friars site.

Drill a hole in the filter????? really really bad idea.

in the bottom plate of the single filter not the element

Scroll down to (drilling bottem of air box) for instructions. You might want to look around here for more info before drilling. I dont remember hearing anything bad but it seems to me that if you rode much gravel or dirt that hole would suck alot of dust into the filter. Also may require a rejet.
http://www.bonnevilleamerica.com/forums/...d9d9443242622c1

Im in the middle of modifying my airbox.. I am makinga filter to fit the larger hole in the top once the filter retainer is removed, should allow about 100% more airflow

Photos to follow

TrOjAn

you can just remove the rubber snorkle from the filter retainer, and use a uni or k&n filter designed for the bike. plus cutting out the bottom portion if the filter and the airbox to get exponitialy more air flow. Dinqua has a post in performance mods all about it.
This will directly affect yor carb setup, so you will need to rejet. Dinqua also has a jet calculator that will get you real close but thats a bit of T&E. I found that his calculator is very close but slightly lean. although it estimated exactly the same as Friar Johns jet calculator.
The calculator told me to go with 127.5 mains I ended up with 130s in. There are a lot of variables so that is very close.

Crikey the snorkels went first day I got the bike.. I have had the insides cut out since day one... my main restriction at the moment is the size of the hole in the top.. which I have now doubled

I have to be careful over here about water getting in.. it rains a heck of a lot here LOL

I would like to see the work you have done to the air box can you post a pic here

More than happy to post pictures, I should have it done by Saturday so will have it how I want, post pictures then

BTW: I got a piece of RAMAIR Air Filter Foam which I will be making the filter from.

cool I hope mine is done then too

Got the filter done today... think it should be ok, heres some photos in case your interested,

http://www.photobox.co.uk/album/536994611

that looks really good I would like to see the filter you are going to use. Did you use the original piece that held the filter in place and just cut it out? or fabricate a new one. Very interesting some of the enginuity on here.

What you see IS the filter, there is a 15mm thick Ramair foam cut to shape and placed between the 2 bits of mesh.

I used bolts slightly longer than needed so they dont crush the foam.

cool.Thats awesome dude.

Terry,

Thanks for that post and pics. Never thought of totally removing the air filter and inlet plenum. Then fabbing a filter over the larger opening and using that only, cool. You could probably open the top up a lot more and utilize filter material to get even more air in. Less chance of getting water in like you would with a hole drilled in the bottom.

Where are you getting the filter material/foam. Does it have any kind of special rating?

This is purely an experiment at this stage, once the bikes back together then I can get some data off it and adapt accordingly.

I have 2 backup plans depending on where the dyno shows I am.

As you say, if I need more air then I can either take half the top off the airbox and use the same idea which would give tonnes of air...

or my personal plan 2:

Where I have cut the inside baffle out make a filter to fit flat inside there, that would then free up the back part of the airbox for tools etc.

If I need to restrict the air I can place a flat bit of plastic under the mesh on top of the filter.. so this way I have many options.

My first idea before I came up with this was to use 54mm rubber pipe to come straight off the rear of the carbs and then have the K&N Pods INSIDE the airbox with the top cut off completly.

I just think this is easier, neater, and certainly cheaper

Watch this space for the results once the 904 kit is on.

I intend using 150 mains to start with and work on from there.. its exciting aint it

I got my thruxton needles today and got them in. now I need to decide on how I am going to modify my air box.

So this is what I did. That a uni foam filter with the bottom drilled out, and the other is the bottom of the air box with 5 1/2 inch holes drilled in. One of the holes chipped as the bit went through. Oh well I guess. I wonder if it is possible to make to big of a hole?
I found some of that air filter foam at a place called Hole Shots. they have two kinds the coarse foam and the two sided. The Guy said you dont need to use oil with the two sided.