stock s40 and it looks like like not much air can get past all the wires and one of those little square tack thingy s   i put there. so thinking of drilling the removable airbox cover i am sure the guys on here have some good ideas so i will wait to get some advice , thx

I removed the Rubber snorkel on top. I had a cam , Supertrapp, modified header, jets, airflow easily kept up.

dave good point .i have to look for the removable thing on the top also what about a few holes drilled on the top of the cover? my airplane has its filter up front and center and actually likes a little water shoved down its intake .it also had a paper filter for many years. just looking for the best way of doing this.thx

hotprops wrote on 09/15/15 at 12:00:50:


I learned to fly in a 1946 8A Luscombe, and I remember the little square air filter being right up front.

I had never really thought about what happens to that filter when it is raining!  

There is an actual scientific term for what you are describing. It's called "re-inventing the wheel".

So when you say you installed a "little square tach thinghy" I am going to take a leap and guess you have one of those cheapo LCD tachometers mounted under the seat? Just laying on top of all the wiring, or is it secured? If that is the case, couldnt you just extend the wire and put it on the fender behind the rectifier/regulator?

Regardless, the engineers at Suzuki designed the air intake for maximum fuel economy and best performance under many different driving conditions. But YOU think your carb needs more air? Are you having performance issues?

If you are a tinkerer and just want to mess with it for kicks, that's cool. having had some carb issues I try to stay away from messing with the air/fuel stuff, but hey.....knock yourself out

I wouldnt think that drilling holes in the interior plastic filter cover would do jack due to the metal cover that goes over the top of it....or were you planning to swiss cheese the metal cover as well? That I think, would be a mistake unless you louvered it and screened it somehow. I'm usually a "if it ain't broke, don't fix it!" kinda guy, but that's just me.

I recently moved my rectifier/regulator from under the seat to the area where the tool bag usually goes. I was worried about it getting too hot so I cut a couple of 2" holes in the chrome cover and installed some vents. I'll post a pic below.
A vent like that mounted on the metal side cover might work and not be as susceptible to rain and road debris.

Have you pulled the snorkel?
If you think it needs air, then it is rich.
How's your plug?

You do realize that for most throttle settings....there is not going to be any difference in performance.  Even when cruising down the interstate at 70 mph you likely don' have more than half throttle...and the stock air cleaner and air box are not causing a restriction.

At some point high in the rpm range at full throttle.....maybe it causes some reduction in the amount of airflow into the engine - I really don't know.  It could be that the CV carb and mild cam really are not affected by the air box.....the only way to know for sure is to do some acceleration testing and find out.  If there is more air made available at high air flow conditions (full throttle and high rpm) - then you may have to install a richer main jet to compensate for the extra airflow.

hotprops wrote on 09/16/15 at 13:09:17:


The puke tube (drain) is on the engine side of the air filter element.....not sure if you will ever get that to read 0.  Insert the hose from the vacuum gauge down through the snorkel so it is on the other side of the filter, and that will show you if the snorkel inlet is causing any restriction....or if the air filter element is the only measurable restriction.

It would be nice if somebody did the same test with the K&N drop in element....and confirmed that it allows more air flow than the stock paper filter.