I know a lot of you have slip ons. Did you have to rejet the carbs for that? I have a '01 ZX9R and I'm working on saving up for the slip on, but in the meantime was thinking about a K&N to get it breathing better. I can hang with my brother's R1 once I'm moving, but it just drags its feet getting off the line...no bottom end power. Should that amount of air increase require jetting or just an adjustment? I'm only dreading the jetting issue cuz I was recently in the carbs getting varnish out. Also jetting seems to be a hit or miss science. Any suggestions welcome.

 

You likely won't get any real increase in "power" unless you increase the volume of gas "flow" to match the increased airflow from a slip-on. One of the main reasons larger displacement bikes have the bottom end, is due to the amountof air and gas (due to displacement) they crank through; more displacement per "bang" equals more grunt. The 9 is down on displacement from an R-1 to begin with. So, if you want to get it on with liter bikes, you at least have to increase the airflow and the gas flow. It's all spark and gas volumeand airflow. A K&N by itself, won't increase anything, because you haven't done anything on the intake or exhaust ends to change the flow. (Think about it.)
When youadd the slip on, depending upon the model, (and the amount of baffling/packing) you'll need to "match" the air flow coming into the cylinders with the flow going out through the pipes/muffler. (The other variable is the diameter of the header/pipes you're using. Larger diameter pipes will give you good top end, but crappy low-mid. Smaller will give you better low-mid. But, that's a whole 'nother subject.) So, to answer your question more directly, yeah; you'll need to re-jet the carbs to increase the amount of gas getting into the carbs to match theincreased amount of air you're running thru the system by adding a slip-on. The jetting is a fairly "narrow" hit/miss, but there are plenty of posters on this site whom you can ask for advice.

 

I adjusted my carbs every day at the track even with the stock exhaust. So I will say yes on adjusting your carbs with a filter and a slip on.

 

Thanks for your help guys. That makes sense. I've done this stuff with cars for years, but this is my first bike. I guess I'm over complicating it. In the end, the basic principles are the very same.