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Air Injection Sys. on US models. Why & How? 8 years 4 months ago #9942

  • trikebldr
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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



Nick,
This really has nothing to do with the quality or the cool factor of the block off plates, but I had a discussion with others of knowledge about the sixes and we discovered that there are many versions of these engines with totally different means of venting blow-by gasses, and some versions of these engines would be in trouble if you removed that ventilation source from the original cover. Some engines have a different location to ventilate the crankcase, but some of the American versions only vent through those original cam covers. Block them off and you will be blowing seals out left and right!
So, it might be wise to make up an instruction sheet to anybody wanting them to be damn sure their engine has other means of ventilation!

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Last edit: by KZQ.

Just made these on the CNC. What do you think? 8 years 4 months ago #9959

  • Nick89
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trikebldr wrote: Nick,
This really has nothing to do with the quality or the cool factor of the block off plates, but I had a discussion with others of knowledge about the sixes and we discovered that there are many versions of these engines with totally different means of venting blow-by gasses, and some versions of these engines would be in trouble if you removed that ventilation source from the original cover. Some engines have a different location to ventilate the crankcase, but some of the American versions only vent through those original cam covers. Block them off and you will be blowing seals out left and right!
So, it might be wise to make up an instruction sheet to anybody wanting them to be damn sure their engine has other means of ventilation!


Good to know, The motor these were made for is from a 1983 ZN1300. I'm not sure which motor it is but it takes 6 quarts of oil and the crank case vent is on top of the transmission.

The two blocked off passages on this motor were air injection ports for the exhaust.

Would you know how to identify these motors? Is it in the FAQ?

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Just made these on the CNC. What do you think? 8 years 4 months ago #9964

  • trikebldr
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ZN1300 (Voyager) motors are VERY different from the KZ motors! About all they share with the KZ motors is their basic dimensions of bore/stroke/cylinder spacing. Their clutches, alternators, left-side cases, right-side cases, back of cylinders, fuel delivery, oil sumps are all different. Having said that, they do share this air system, but only on the U.S. models. And, you are right that that is an air feed system to the exhaust for better emission control.
But, this system is rather sensitive, and any changes can affect idle and power. There is no "pump" to force air through this system except for the fact that the feed port in the exhaust port is positioned such that any exhaust movement past it creates a vacuum (the same way that air flow through the venturi of a carburetor draws fuel into the airstream) that draws the feed air into the exhaust stream to allow continued burning of the waste gasses.
There is a small reed valve that must be kept clean or it can allow backfeed of exhaust gasses into the carbs/injector-bodies if it doesn't check the backflow. In theory, blocking off the air flow with your plates should only change the idle a tiny bit since it is only drawing a small amount of air from immediately in front of the carb or injector body inlets.
In the main manual the theory of operation is shown on pages 180-181, and there is a detailed illustration of the system on page 3-25 in the supplement manual for the ZN engines. This system is only on the U.S. model engines.
I'm fairly adamant about leaving a well-running system alone as the engineers designed it, unless your goal is all-out racing where street-ability is not important. This syetem taps into the main air intake system and will affect it if modified. Here's why:
THis system draws it's air from AFTER the air cleaner on the bike. So do the carbs/fuel-injection-bodies. The air cleaner does create a pressure drop in the air just in front of the carb or injector bodies. So, we have the carbs drawing air from this point as well as this exhaust-feed system. Both systems are affecting the overall "pressure" (actually, a slight vaccum!) right in front of the carb inlet. So, now let's remove the draw from the exhaust-feed system. There WILL be a change in the idle due to a change in this vacuum. Also, if, as the book says, that reed valve, or the vacuum switch, are not in good shape and allow back-flow leakage, you will get some very erratic idle results. We have read several times about how an engine will change idle a lot as it warms up, and sometimes cannot be slowed down even by backing off the idle screw. If the reed valves are warping from heat as the engine warms up, this will change the idle a lot, too, as it will allow more air flow into the exhaust ports.
Your block-off plates will eliminate this system, and it's attendant problems, altogether, but you will need to make adjustments, especially to carbureted models. With slightly less vacuum at the carb inlet, the jetting might need to be adjusted. Not sure if/how the fuel injected engine would be able to be compensated since there are no sensors for this change. I suspect there would be a lean-out effect since there will be less vacuum, hence a denser air supply feeding the injected system.
Oh, what a complex web we weave when we try to clean up our air!
Nick, thanks or presenting your plates! It has forced me to re-examine the system they affect and really come to understand the hows/whys/whats and why-nots of this system, and possibly why my '85 ZN slowly increases idle speed as it warms up! AND, I have learned that this system has nothing to do with venting the crankcase, so my apologies to you about my suspicions about the effects of your block-off plates.
(as he takes a couple of bows and steps down off his soap box!)
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Last edit: by trikebldr.

Just made these on the CNC. What do you think? 8 years 4 months ago #9975

  • RickG
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Just a Short Hi jac of the thread.
So it was only the US models that have this system is it? If So that makes the A1 I bought with the Rickshaw on it a US model and does explain why it is so much earlier than my original AI that I have owned since virtually new and was one of the first Z1300s in Australia.
Live your life so that the Westbro Baptist Church will want to picket your funeral
Z1300 A1 x 2

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Just made these on the CNC. What do you think? 8 years 4 months ago #9979

  • globemaster
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Facts:
1. The clean air system was only on U.S.A. models.

2. It has nothing to do with the crankcase vent system. Although, some fumes from the crankcase do get pulled through the clean air system and into the exhaust because the crankcase vent system vents into the air cleaner housing and the clean air system draws its air from inside the filter box, after the air passes through the air filter.

3. The clean air system, does not make enough change to the partial vacuum inside the air filter housing to affect the idle. The vacuum switch valve will vary the air flow through the clean air system in response to engine vacuum, and cuts it off entirely during high engine vacuum. Additionally, the amount of air flow varies with pressure differentials in the exhaust system. PROPER removal of the clean air system will not change the idle or any other aspect of the fuel mixture. Note emphasis on "proper".

4. The clean air system can cause erratic idle problems if the air suction valves (reed valves) leak. This allows exhaust gas to enter the air filter housing and mix with the air entering the intake. This has the same effect as a stuck open EGR valve.

5. A faulty vacuum switch valve that does not cut off air flow during high engine vacuum will usually cause backfiring during deceleration.

Hope the above helps.
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Just made these on the CNC. What do you think? 8 years 4 months ago #9980

  • globemaster
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RickG,

This is for you. Yes, unless some wanker placed a U.S. cylinder head cover and all the bits of the horrid clean air system on your A1, it is definitely a U.S. KZ1300.

In the 1980's, it was my pleasure to make several visits to your lovely country. I was surprised to see the cylinder head covers of the Australian Z1300's to apparently be one solid piece. No reed valve covers.

The Canadian versions do not have the clean air system, and thus, no reed valves. They do have the reed valve covers, but they are different from the U.S. covers. The air inlet nipples on the rear of the covers are short, vestigial protrusions with no openings.

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