Hi All,
Here I am again with this air filter thingy. Was wondering about drilling the cover when I put it back on. I've read about the pros and cons and when I looked at the back of the filter itself I wondered if drilling was really worth it. That screen and the metal piece with all the holes in it seems to be pretty limiting. Has anyone worked any mathematical figures as to the amount of air coming in through the air tube and the amount that can be processed through the filter assembly itself?

I suppose it's maybe all variable but really questioned my delayed decision as to whether to drill or not. What meager numbers that I could come up with were the filter in and out figures (27.75"sq. front and +/- 15"sq. back). I guess the critical number would be the area of the incoming tube and how much air it can process; that's the part I wonder about but don't know. Anyway... any further thoughts???

I did the air filter box modification about three years ago and except for a little more throaty sound I can't tell you for sure that it made any difference.I also removed the tube from inside the box.Before drilling I went the local ACE hardware store and purchased plastic plugs that I could fill in the holes.I believe I used a 7/8 hole saw and purchased 1'' plugs to fill in the(6) holes.
Experiment on some material before drilling out the box.My main concern was running in a lean condition.I have removed the spark plugs on occasion and they appear normal. The MAP sensor should take of this. Also if your s/wing has a 02 sensor this would even be better. Howard

Thanks for the reply Howard,
I decided to put the filter back in that I'd cleaned up plus drilled a few (six?) 1/4" holes on the flat just above the "bulge" on the case; more for curious experimentation than anything else. Anyway, the engine started fine and ran well too; still no dying out like I experienced a week ago, plus wanted to prevent any possile 'lean' problems like you mentioned.

If I get real lucky, maybe the weather will warm up a bit and I can take it out for a real test. Will keep y'all posted.

In talking to another tech type, it was agreed upon that several large holes are less desirable than many smaller holes. It's all about turbulence and laminar flow. Can you have too many small holes? Maybe if wet weather riding is an issue. You can always duct tape over some holes if for some reason you're not happy. If you're running a stock engine and exhaust, there really is no need to drill the airbox. The K&N lowers intake restriction, but the limiting factor is still valve sizes and exhaust restrictions. The biggest contributor to air flow is getting rid of the stock muffler with its honeycomb catalytic converter. You wouldn't believe the force and volume of the exhaust when you go to a straight through muffler. Each exhaust pulse literally pushes your hand away from the outlet when using a performance muffler.

I doubt it but I'll ask the question anyway... Can the stock SWing muffler be modified in any way without destroying the basic shell???

What year were the mufflers made Cat?