How to make neat holes in airbox? Can i use a hole punch or would it crack the plastic? A sheet metal punch, the kind that you drill a pilot hole and then tighten the tool and...?
Probably because the OP imagines the trained engineers who designed the air intake botched the job, though those engineers had access to a dyno and more than likely spent many hours making sure the airflow was optimized for the resonant cavity of the air box, ( think of Helmholtz and you will be on the right track). How likely is it that the engineers did a bad job and someone who needs to ask how best to cut holes in the air box will do a better job ? Sort of like leaving an orangutang in front of a typewriter and waiting for the sonnets of Shakespeare to be produced ( don't hold your breath waiting for anything intelligible to come out of that typewriter ). .
Your right,it seems like a great idea to swiss cheese your airbox,till that first real dusty ride and the filter plugs or passes dirt. Or you just cant quite get the jetting right no matter how much you mess with it,or the new noise produced makes you crazy. Its fun to second guess engineers though.
you guys really think every bike shipped from the factory is tuned for maximum performance, or do you think the engineers in question might have had to consider factors like fuel economy or emissions standards or rider-friendly power delivery, or a hundred other factors? I've owned two bikes where airbox mods were a well-documented and much-utilized improvement. It happens. now, back to the original question: step drill for small holes.
i havent tried it yet but try a piece of metal pipe the diameter you need and heat the end and push it through the plastic. maybe try it on a extra part first though.
Hole saw or step drill, either one . . . . but back up the plastic with something (soft wood, perhaps) or you may create a hole that is larger than you intended . . . . . (depending on the plastic)
Step drill....they are cheap at harbor freight. I think mine will go to an inch. Anything bigger and out comes the hole saws. But you need backing for the last otherwise you'll tear the plastic. You can countersink the holes....may help with airflow. Smaller holes with side access, out comes dad's old airplane tools, namely the sheet metal punch. I think HF has cheap replicas of that tool.
And remember to keep the drill speed low so the friction doesn't melt the plastic and ruin your nice, clean edge.
Pic a size and aim well: Gotta say I'm in the camp of "the engineers knew what they were doing" though.
Hole saw. As for the legitimacy of doing it, it just depends. The engineers, as mentioned, design an airbox for a wide variety of factors. Noise is a big one. On my Triumph Scrambler, the airbox mod really helped with an open exhaust. Jim
