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The mistery hole 30 Dec 2021 11:50 #859832

  • shamal
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Can someone please explain what the hell is this hole near the exhaust port in the head of the gpz/ zx750? And why is directly "vented" in a hole in the cam cover? 
1983 kz 550 h
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The mistery hole 30 Dec 2021 11:57 #859833

  • Mikaw
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It’s emissions control item. Kawasakis clean air system. Reed valves in the cam cover allow air into the exhaust to help burn excess fuel to pass emissions. 
1976 KZ 900 A4 kzrider.com/forum/11-projects/613548-1976-kz-900-a4
1976 KZ 900 B1 LTD
1978 KZ 1000 B2 LTD
1980 KZ 750 E1
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The mistery hole 30 Dec 2021 12:00 #859834

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It's an air bleed port for the US emissions system.
Basically a dodge by Kawasaki to pass US emissions laws by bleeding air from the intake through a one way reed valve sited in the cam cover and into the exhaust port via that hole.
This was done to reduce (dilute) the parts per million count of toxic particles in the gasses being expelled out of the silencer.
 

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The mistery hole 30 Dec 2021 12:22 #859835

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It's an air bleed port for the US emissions system.
Basically a dodge by Kawasaki to pass US emissions laws by bleeding air from the intake through a one way reed valve sited in the cam cover and into the exhaust port via that hole.
This was done to reduce (dilute) the parts per million count of toxic particles in the gasses being expelled out of the silencer.


 


Um, not exactly.  When the exhaust leaves the combustion chamber it's still extremely hot, and injecting fresh air into the exhaust stream encourages any remaining raw fuel to burn while in the exhaust pipes.  Tons of cars in the late 60's and through the 70's had air pumps for the exact same reason.  Kawasaki's solution was very ingenious because it consumed zero power, unlike an air pump.  One downside, especially for guys running headers, is increased exhaust temperatures.  A small price to pay though.

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The mistery hole 30 Dec 2021 12:38 #859836

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Ok thank you for the response but i still dont understand, since my kz750 has the cam cover without the reed caps on it... So, is this system just completely useless on my model? Should i check something in the cover? I had an air pulse coming out front the left first one when engine was idling
1983 kz 550 h

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The mistery hole 30 Dec 2021 12:44 #859837

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Ok thank you for the response but i still dont understand, since my kz750 has the cam cover without the reed caps on it... So, is this system just completely useless on my model? Should i check something in the cover? I had an air pulse coming out front the left first one when engine was idling

 This photo shows the air injection port being tapped so it can be plugged with a grub screw.  Does your head have these ports?  If so, you should plug them.  I did that, and ran a Turbo valve cover, which doesn't have the air injection junk on it.  

P1020559 by nessism , on Flickr

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The mistery hole 30 Dec 2021 12:54 #859838

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Yes i have the ports as you show. I think once the cover is on , the cover itself can be a "plug" , or i am wrong? What can cause leaving the ports unplugged like you did? 
1983 kz 550 h

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The mistery hole 30 Dec 2021 12:59 #859839

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my kz750 has the cam cover without the reed caps on it... So, is this system just completely useless on my model? I had an air pulse coming out front the left first one when engine was idling

Yes! the system is dormant without the reed valve cover.
The head is still drilled to the exhaust ports and you will feel a back pulse from the exhaust with the cover removed
You don't need to tap and plug the holes if you already have the correct cover.
Once the cover is installed it should have blanking lugs which block off the drillings

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The mistery hole 30 Dec 2021 13:43 #859841

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This pic describe the "mistery hole" system.

 
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The mistery hole 31 Dec 2021 07:14 #859858

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Personally, I would install the grub screws anyway. The extreme pressure changes can cause the cam cover gasket to leak, allowing oil to be drawn into the exhaust port from the camshaft area.
1982 KZ1000 LTD parts donor
1981 KZ1000 LTD awaiting resurrection
2000 ZRX1100 not ridden enough
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The mistery hole 03 Jan 2022 12:00 #859981

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I don't know what size the holes are but these fit the ZRX engine. Kwick lists the size.
www.kwick.biz/product/noflo-emission-pair-block-off-plug-set/
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The mistery hole 03 Jan 2022 19:57 #859988

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I don’t think those will work on the KZ engines as there is no shoulder for the plug to bottom on. They work a treat on the ZRX, though.
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