TOPIC:

Globemaster, I take exception your "fact" #3. This morning I went out and ran both of my ZN's up to temp and then clamped off the hose connecting the air box to the inlet side of the vacuum switch, and both bikes increased their rpm by 150rpm, at idle. My '84 has just 27,000 miles and is like a new bike, but I wanted to see two results alike before accepting it's results. Since my '85 did the same, I trust that both bikes are in good shape with this system and both are a valid test.

I think you underestimate just how much air flows through this system. Remember that it's intended to complete the combustion of unburnt gasses coming out the exhaust, so that's quite a bit of air.

As a side experiment, I also removed the air cleaner (a recent NOS replacement) from my '84 and it increased about 75rpm at idle. Not much, but significant. When I get more time I will add a tap point to hook up a manometer to really measure the inches of pressure drop in the air box just in front of the carbs/injection-bodies.

trikebldr, Your exception to my #3 is correct regarding fuel injected engines. I was basing it on my experiences with carbureted KZ1300 engines. I've removed the clean air systems from 3 KZ1300's and in each case, there was no discernible change in idle speed. I have zero experience with fuel injected ZN1300's.

I apologize for not considering how sensitive fuel injected engines are to the amount of air entering the intake tract. Typically, the idle on a fuel injected system is set by an idle air bypass system. This system allows air to bypass the air flow meter and the throttle plates. To increase the idle speed, extra air; but no extra fuel was allowed to enter the intake manifold. On most Bosch licensed fuel injection systems of the 1980's, the idle air bypass was a screw which was turned in or out to decrease or increase the unmetered air that entered the intake manifold. Very small increases or decreases in the amount of air fed through the bypass system will change the rpm. The clean air system on your ZN1300 is acting as a de facto idle air bypass system.

On a carbureted engine, idle speed is increased by opening the throttle slightly, and allowing more air and fuel into the engine. If the clean air system could significantly alter the air velocity in the carburetor venturi's, that could alter idle rpm. In my admittedly limited experience, this does not occur. I allowed my KZ1300 engine to warm up and experimented by letting it idle with a new genuine Kawasaki air filter element and then with the air filter element removed. No difference in idle rpm.

By removing your air filter and observing the 75 rpm increase, you have illustrated 2 things:

1. The air filter element has some small amount of restriction.

2. This small amount of restriction is enough to slightly lower rpm by reducing the amount of air entering the intake manifold.

Air flow restriction through an air filter element would have the opposite effect on a carbureted engine. It would act like a choke, enriching the mixture and raising idle rpm.

There's no air bypass on the ZN engines for idle speed adjustment. It's pretty much like the carb models, with mechanical butterfly positioning. Basic idle speed is set with a knurled knob underneath the right injector body, and cold-start speed is a simple lever on the left end to kick the linkage just a bit.

But, I do know what you are saying about air-bypass systems. I had a Subaru that used a nichrome wire MAS and when that wire got older the idle went to crap unless you "polished" the wire clean again! Kawasaki got it right on the ZN Voyagers and the later KZ's with injection. It's a very simple system with just three sensors to tell the controller how much to squirt! Easy to remove,clean and test, too. A bit dangerous (fire hazard!) to really test the injectors, though!

This part is for Nick, another of the big differences in the carbed engines and the injected engines is the difference in intake runners. COMPLETELY different in spacing and length. So, heads are not interchangeable.

Globemaster, this has inspired me to look into total removal of the clean-air system from my test-bed ZN to see how performance is affected. By reburning exhaust gasses it increases pipe temps and promotes early deterioration of the double walled headers. It also causes additional heat to be radiated from the pipes right behind the radiator, and as we all know, the Voyagers are notorious for stop and go overheating. I wrap my head pipes with heat tape until just below the radiator to eliminate this issue. But, I may try eliminating this clean-air system to see how much the bare pipe temps drop. I can't see how it would affect performance at all, though, except it may burn just a bit dirtier. Oh, well, so do the rest of them around the world! If my reed valves ever go away on me, there's no choice but to remove the system.

trikebldr, Thanks for the explanation on the ZN1300 idle adjustment system. Kawasaki did it right, much simpler than the air bypass systems usually encountered.

I never even thought about the excessive heat generated in the exhaust pipes by the clean air system. It must be significant and as you pointed out, can wreak havoc on the exhaust pipes as well as contribute to overheating.

You are correct. The rest of the planet never got the clean air system (lucky devils). Removing it won't make any difference in performance IF the system is functioning properly. What removing it does accomplish is eliminating the possibility of problems caused by the system, especially due to malfunctioning reed valves.

As you inferred, finding new replacement reed valves or an air suction valve is almost impossible. They have not been available through the Kawasaki parts system for years. They do sometimes turn up on eBay for astronomical prices.

Hi Folks,
Nick89's thread about his CNC air injection system block off plates is still in Daily Chatter.

See: www.kz1300.com/index.php/forum/daily-cha...-my-block-off-plates

It's a good thread but as it seems to have developed into an in depth discussion about the Whys and Hows of the Air Injection Systems on US 1300s, I though it would be more useful and available if the latter portions were split off into a new thread here in the engines forum.
With apologies to Nick, TrikeBldr and Globemaster.

Here is their new thread.
Enjoy
Bill

And I wanted to note That I'm am using kz1300 carburetors on my ZN1300. The wiring harness for the fuel injection was destroyed beyond repair.

If I ever want to get the FI working I will need to build a harness from the ground up or find one on ebay!