2 into 1 exhaust a cause of extensive re-tuning?

I understand how disruptive to a bike's tuning it is to replace the airbox with "pod" style filters. What about a carefully selected 2 into 1 exhaust? At first glance I'd expect there would be more back pressure but if a more free flowing muffler and or larger diameter exhaust piping was chosen, could a careful owner arrive at the same back pressure and not bring about monkeying around with different size jets and mixture adjustments? I also wouldn't want to screw up access to whatever I need to routinely service under the bike. I'm thinking the weight loss aspect would be appealing to offset other improvements I might make on the bike? How does removing all the exhaust from one side of the bike affect handling?

My questions pertain to a 440 A-1.

It's pods that cause all the havoc.  An exhaust change won't, including as related to handling.

I agree that changes to the intake (air filter) do require more jetting/tuning that most 2 into 1 or 4 into 1 exhausts do. Usually the change in exhaust is as stated loss in weight and therefore in change in HP to weight ratio. But  there are times where adding  the exhaust does require changes.  If you have not seen this link I would suggest you read it for some more info on the subject. Not attempting to indicate it is the one and only truth, but it does add some more info to think about. 

www.cycleworld.com/story/blogs/ask-kevin...t-system-is-changed/

It could be that you may not need to change, but the new exhaust may shift your torque curve and insert flat spots where you didn't have them before. Probably best not to worry about it.

If you were racing the bike then, you would need dyno time to figure out where to put the collector and if you need any steps in the pipe to tailor your negative and positive exhaust pulses. Also, figuring out your pipe diameter size to keep your mach index in range and keeping heat in the pipe to keep your exhaust speed up.


Kevin Cameron is pretty amazing gd4now.

The KZ 400C came from the factory with a 2-1 exhaust. Perhaps it would be helpful to compare the factory jetting for the C to the 400 A or B to see if there were any differences

That is an excellent idea!  Thanks for sharing that !

Totally agree about not worrying about changing "flat spots". Worse case scenario ... having to remove a 2 into one exhaust and re-install the stock exhaust wouldn't be all that bad anyways, even for a glorified parts replacer like me. The Kevin Cameron piece on exhausts in "Cycle World" is a definite keeper and "gd4now" is a saint for sharing it.

Cameron is a gifted technical writer. It's hard to write to every level of mechanic, engineer or service person but he seems to find that sweet spot. I fully understand most of it and with the laptop I'm reading it on, I can simply google the concepts I'm unfamiliar with and have a familial understanding with the rest. Riding my bike is the best part but I do enjoy learning about some of the physics involved in driving, designing and building a bike. Thanks for your help!