KZ650 Intake/Exhaust Performance Mods?

Okay, assuming I get my carbs sorted out - which I'm sure I will - I'm wondering where to go with this bike for best street performance.

The usual thing, I know, is pod filters and a 4-into-1 pipe, along with some jetting changes, and I know this would make the bike significantly faster. On the other hand, most of the improvement would be top-end power, and I could hardly care less about that. I care about 4-8krpm performance, the midrange pull that you can actually appreciate on every ride; and I don't want to lose low-rpm tractability.

I also, frankly, don't like the noise.

So I am wondering to what degree the pod-and-pipe thing actually improves midrange performance, and what the best way is to improve performance in this range without adding noise.

Some things that have come to mind (engine mods are potentially to come later) are that a K&N drop-in filter, which my bike already has, may flow just as well as pods at any normal rpm and may actually make better power at lower and mid rpms than pods. Has anybody ever been able to quantify the changes made to a stock motor with various different intake approaches?

Likewise, the stock exhaust is probably too heavy but might flow perfectly well, and it's nice to keep the look and the sound original if possible. Does anybody know?

If it turns out that a 4-into-1 really does without a doubt improve power in the range that I want to improve it in, does anybody know of a quiet 4-into-1 system that still flows well? What about the option of a typical 4-into-1 pipe, but with a quiet muffler attached? I know part of the improvement from a pipe is from flow (=loud or =large muffler volume) and part is from pressure wave tuning; header length and back pressure and all that. Perhaps there is a good compromise that will give good power and stock-level noise control.

As before, thanks to all.

- Glenn Carpenter; Golden, CO

The only way I can think of to increase the midrange without increasing the noise level is to install a Wiseco 810 kit in a early 80's KZ750 cylinder block on your motor and have the valves lapped to get a really good seal.
Like you said, the pods (which I don't particularly like anyway) and the 4 into 1 pipe, is for high rpm gains.

There's no replacement for displacement

Yes, definitely interested in future internals work including displacement. Still, intake and exhaust mods alone are probably worth something on this motor and I wonder whether anybody has quantified that.

The new ZX14 has 4-2 pipes. I am sure the article I read said that 4-2 would breathe better than 4-1. I think a 4-1 has more of a weight saving factor going for it. There is supposedly tons of gians to be had from degreeing in cams. Maybe go whole hog on 4-1 and pods then play with cams to get gains back down in middle range. Maybe?

Yeah, I'd do that except for the noise thing. I actually don't mind the noise and like the sound, but a few 7krpm passes past peoples' open windows on mountain roads and I just feel like too much of a jerk.

Degreeing the cams is a good idea. I bet you can buy slotted sprockets off the shelf for these bikes. I'm really tempted to look for a way to get a 4-into-1 setup that I can use with a quieter muffler. Actually making it work, with the right bends in the pipe and a decent-looking result, would be the trick. Many people don't realize that you can get as much flow as you want with as little noise as you want, but the tradeoff is muffler volume. I think you're right about the weight vs. flow thing with 4-into-2 vs 4-into-1 systems. But aside from flow, tuning of the exhaust for cylinder scavenging requires that all four headers ultimately are joined. That is why factory 4-into-2 systems all have some sort of crossover or power chamber between them, including the stock system on my KZ. I'd almost be inclined to stay with the complete stock system, except that I've seen enough indicators that aftermarket systems really do help on these bikes to believe it. Also wouldn't mind losing the weight and improving the look, naturally.

I'm pretty sure a free flowing drop-in filter, which I already have, will flow as much air as pods on these bikes, but I don't know for sure. Would love to hear from somebody who does, one way or the other....