Airbox Wire Mesh question

[RING_DING]

The wire mesh screen that's fixed to the inside of the airbox is in really bad shape, and starting to come away. It looks like two layers, and it will be a bugger to replace even if I could find the right gauges of mesh. Apart from keeping foreign objects from being sucked into the carbs, does this mesh serve any other purpose? I would think that the foam filter with a good seal around the edges should do that job just as well. Thoughts/advice appreciated!

[Suzsmokeyallan]

Roy that double mesh is a royal pain and I often wondered if it was overkill with two layers, however if yours is coming apart take it out before a piece goes into the engine.
Once you are using a filter with a good seal all will be well so I would not worry about it being removed. Its a severe restriction to the intake and so removing it will also allow the engine to breath freely.
Your post just reminded me to rip out one on an airbox I'm restoring so thanks for the reminder.

[Suzsmokeyallan]

Roy I went at the airbox today and have the screen out with the edge surround of the frame it sits in. The next step is to cut out the small remaining lip of metal that meets up to the section where the filter base sponge sits.
I'm going this route so the extra metal around there does not continue to block airflow. Once its done then media blasting and primer is the next step.
I will get a photo or two up as soon a I can take them so you can see what I did.

[Suzsmokeyallan]

Here is the screen updates in photos, this job is very time consuming and tedious to do so the end results look neat.
You have to use an angled head tool on a Dremel moto tool with cut off wheels to create this level of final finish.
The space is very limited and I also had to modify the angle head attachment to gain some extra leverage being the box side openings are very limited in width.
I cannot figure out the logic of this design, this is very poorly executed and an extremely convoluted way of getting air efficiently towards the carbs
After I had the metal sections removed and everything ground level, I bead blasted the airbox and primed it in the grey you see here.


The restrictive screens frontal section in a stock airbox, its about a half inch from the front and most of it is not lined up with the intakes.


The rear facing section of the restrictive screen frame.


The frontal view with the screen and metal surround frame now removed.


The screen surround frame has a rim with a lip thats spot welded in, its near impossible to remove this with the airbox assembled, so its best to cut it off at the bend and leave the lip in for support.


The section in front of the air filter now has more room for incoming air to circulate into the three carb bellmouths.


Another view of the freed up space thats less restrictive than before.

[tz375]

Allan,

I was wondering how much of a flow obstruction that mesh is and what the effect on jetting might be. We can speculate one way or the other, but it might be a good idea to keep an eye on mid throttle jetting after the modification - just to be safe.

[Suzsmokeyallan]

Richard those thoughts also crossed my mind too due to less air restriction at the bellmouths, so we are both thinking the same way.
The turbulence created from the dual screens is now gone, so theoretically the slides should lift more efficiently, equaling an improvement in throttle response.
Some plug readings would be in order to test the vital mid throttle setting as well as both sides of it.
If its off enough you may actually be able to "feel it" as a run lean surging.
Either way with the mesh and frame gone its a vast improvement over the original design, so we shall see what it does.

[RING_DING]

Wow Allan, you've really gone the extra mile with that! I have removed the mesh screen from mine, but I think I will leave that lip alone for now. Even just removing the mesh will improve airflow. It really is a terrible design when you look at how much the frame blocks off the ports on either side. As Richard points out we'll need to keep an eye on the jetting.

[Suzsmokeyallan]

I thought you would like to see this latest airbox update Roy, and yeah I ended up taking it to the next level and it cost me a fair amount of time to get it looking like that.
The thing is it turned out so impressive looking for improving airflow I now need to do one for another bike.

[RING_DING]

I've been running the JDM bike with the mesh screen removed from the airbox. I noticed that there is a slightly louder intake "honk" but I sense the bike is breathing more freely. The spark plugs are a much better color now (was running quite rich) and I have not changed anything in the carb setup. She picks up much better through the rev range and really takes off above 5000rpm. I'm very happy with the result, but I'll keep an eye/ear on things just in case.
If anyone plans on doing this mod to the airbox, I would advise be very conscious of mixture before vs. after. If you were on the lean side before, you will need to make some carb adjustments to compensate.

[Suzsmokeyallan]

Thanks for the carb jetting info Roy, I recently did another airbox and have got it down to a quick process. I can do them in a very efficient manner with minimal time and effort.
I knew the intake roar would increase a bit with the airbox freed up; something I don't mind as you already get a "honk" as you call it, with the BS40s from the restrictive double screens.
At least now you get a throaty performance result where as before, all you got was noise and not much action.

[ArticusMax]

Hello Allan,
I am working on my GT750 airbox now. All the rubber foam on the airbox is disintegrated. While I was working on that I thought I might as well do the screen mod you did.

* Do you still use the stock air filter after taking out the screen? My air filter had the "filter" material replaced by the previous owner. He used some kind of green 'mystery' foam. I have no idea if it is proper or not.

* Do you have any recommendations for replacing the "filter" material?

* I am missing the little clip to secure the filter to the air box. Do you have any experience replacing that clip with something else?

Best regards,
Art

[Suzsmokeyallan]

My airbox mod allows full use of the oem filter case so nothing changes there, its just that you are removing the restrictive surround frame/mesh material in front of the section where the actual air filters frame sits onto the airbox case.
The sponge trim on the actual airfilter case is usually hard or ripped so its best to replace it by making a new one out of some sponge of similar thickness.
You don't have to put it back on the airbox case, you can also stick it to the face of the airfilter case itself to make the job easier.

The main airfilter sponges themselves are not available separately from Suzuki, you can buy sponge and create one by making a back and sides to size then bonding them together.
Original filters are a fine grain grey colour sponge about 3/4 of an inch thick consisting of a back and a surround thats bonded together.
Many dirt bikes use a similar material sponge which you can buy from Unifilter to make your own.
The sponges are however available in the UK but the price isnt cheap at about 30 quid for the replacement sponge itself.
I asked "Cruizin image" in Japan if he planned on offering any at his ebay store and he said nope, so that idea went south.
For the holding clip you can buy an eye hook and cut it open just enough so it fits in like the original type then cut off the excess threads and use a nut.
This way your little mod makes it look just like the original ones did.

[ArticusMax]

Great info Allan,
I got lucky and was able to push my double screen out by hand. Only managed to poke myself a few times with some stubborn wire strands that didn't want to get removed.

I'll contact those guys in UK for the foam "in for a quid, in for a pound" they say!

Cheers

Art

[Lorenzo]

The "sponge" is open-cells polyurethane foam and apart from the eventual thickness, which should match the OEM, what matters is the porosity, measured in PPI (pores X inch) and for our applications a 60PPI should do;

[ArticusMax]

Thanks Lorenzo!