exhaust cross-pipe

How important is the cross-pipe connecting the L/R exhaust pipes near the center-stand? I notice that MAC exhaust I've seen on E-BAY doesn't have it. I want to repair some corrosion holes on my pipes and it would be much easier if I could just eliminate the cross-pipe all together.

Would this move require re-jetting, even though I'm still using stock exhaust?

What does that few inches of pipe DO anyways for a twin-cylinder engine?

Hey indytwin,
The cross over pipe improves top end power. Motorcycle manufacturers added a crossover pipe even in the late sixties. I doubt that eliminating a cross over pipe would affect jetting enough to force you to change it. You'll have to keep track of the plug color to know what your engine thinks of the new pipes.
KZCSI

Post edited by: kzcsi, at: 2005/11/04 09:38

I going to guess it's more for strength on the pipes for that small a displacement twin.

Not bike related, but read here:
www.corsaperf.com/crossover.htm

I noticed that on Harley exhaust systems (2 into 1) many of the Sportster aftermarket systems have a crossover pipe coming off the head pipes to equalize pressure I guess. They say it adds to top end as has already been pointed out. Most of the older stock KZ systems have a crossover pipe. The stock system on my Voyager has one... the strength theory also sounds pretty good as the stock Voyager system probably weighs 40-50 lbs and if you undid the rear mount bracket would be in danger of cracking without the crossover to brace it... since this is a 4 into 2.

This site:
www.akrapovic-ai.si/main/company/ourstory.htm has some good reading on exhaust technology, and the addition od crossover tubes closer to the cylinder head, but not farther downstream.

My little brother ran a 4-2 system on his GPZ750A1 without a crossover pipe with no noticeable differ in power or smoothness, only a slightly more offbeat engine note.
On a side note I'm gonna post a dyno graph for my ZRX11 which shows why I choose to use Akrapovic headers rather than the very good looking Kerker megaphone system.

I could have lost 8bhp or so by choosing a more stylish system, but no whats the point? I know it's good to work with what you have but any system using stock sized bores can never deliver the goods, so if you're happy weld away and spend the money saved on havin a good time wi ur KZ!

I had a exhaust system off a first year LTD and it didn't have the cross over. After that the cross over has been on anything i've seen.
I didn't read the article posted on exhaust technolgy but from what i remember the cross over equalizes the pressure and helps balance the pulses of the two pipes.
Instead of power stroke and then pause you have power stroke power stroke power stroke power stroke. That is on a four cylinder bike.
So you always have a equal pulse pulling the spent gasses out of the cylinder that just fired.
With a four into one the pulse is as good as you can get. (My thinking)
On a exhaust that has the No.1 and No.3 sharing one pipe and No. 2 and No.4 sharing the other the theory is that No. 1 pulls the gasses out of 3 and No.2 will pull the gasses out of No.4
I think they look good with the cross over but they loose that distint Kawasaki four sound.
Does this help any? There is a lot to digest when it comes to exhaust.
You would be better off to repair your cross over. Roy :blink:

It is early and i am bored. roy

Post edited by: roy-b-boy-b, at: 2005/11/05 08:38

The benefit of a crossover pipe to OEMs is that they can use smaller mufflers to meet noise regulations. With a crossover pipe, the exhaust flows through two mufflers instead of one. The larger effective muffler volume quiets the exhaust note. A performance increase is also possible if properly designed.

Ron

The main reason for a cross-over is for back pressure & a quieter exhaust note. Power is actually ever so slightly increased (if anything) if removed.

What about open pipes? I could cut out the corrosion holes by just hacking the pipes... Would that require re-jetting?

Open pipes will result in absolutely no packpressure, and will move your powerband way too high in the rpm range. Tuning your exhaust is an art in itself. You need to figure out where your engine likes to run, where you'll be using that RPM, and the kind of riding you do first, then work from there. If you want to take it to the track(1/4 mile), to compare the differences from stock to open, I'd highly recommend it, but don't destroy the stock system. Buy another used one first and give it a try. Keep watching ebay, and wait for the right price. I got a good used Vance & Hines off ebay a few weeks back for less than $85.00.

I am also going to comment on the stock exhaust cross-over pipe. Maybe it also allows for ease of oil and filter changes, and centerstand clearance too? Why didn't the factory make 4-1's from the start? I think it's budgets in building the bikes.

I wish I would have stayed in college, and finished my degree in Mechanical Engineering. This would be a great to actually be able to show test results in exhaust systems like this:
www.tfxengine.com/software7.html
Louder isn't always better, but you gotta have a little sound so they hear you coming, right?

Post edited by: CoreyClough, at: 2005/11/07 09:22