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Trying to figure out the air screw 79 KZ650BE ? Need an o-ring ? 07 Sep 2023 09:59 #889134

  • kz650guy123
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I need a screw with an o-ring I guess.
I have been trying for years to get the air screws on my 79 KZ650BE set right. These vm24 smog carbs had the air screws plugged with a cap.
The screw itself does not have an o-ring on it. Never did have an o-ring. There isn't even a groove for an o-ring.
I'm thinking that all the trouble I've had with this was air leaking past the threads. I would put a little grease on the threads to prevent binding.
Then I could almost get a good idle. But it didn't click with me that, that was the problem.
I put a glob of grease in the hole above the threads. Now seems to be running pretty well.
Does anyone know the part number for a replacement screw with o-ring.
If needed I will post a picture of what my screw looks like.
Thanks

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Last edit: by kz650guy123.

Trying to figure out the air screw 79 KZ650BE ? Need an o-ring ? 07 Sep 2023 10:25 #889136

  • ckahleer
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Partzilla shows an o-ring p/n 16038-024
94 KE100
81 CM200t
82 KZ305
85 VT 500c
85 VF1100c
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Trying to figure out the air screw 79 KZ650BE ? Need an o-ring ? 07 Sep 2023 10:38 #889137

  • Warren3200gt
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Plumbers ptfe tape on the male thread before screwing in will stop any air bleed in or out permanently. 

Z1000J2 somewhat modified!

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Last edit: by Warren3200gt.

Trying to figure out the air screw 79 KZ650BE ? Need an o-ring ? 07 Sep 2023 10:52 #889138

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Thanks ckahleer I'll look up that part number.
Warren the ptfe tape is an idea. But I would be afraid that would fall into the carb ?

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Trying to figure out the air screw 79 KZ650BE ? Need an o-ring ? 07 Sep 2023 10:58 #889139

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Ckahleer thanks for the part #. But that is only a o-ring. As I stated in the post my screw doesn't even have a groove for an o-ring.
What I need is a replacement screw WITH an o-ring on it.
That's what I'm having trouble finding.

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Last edit: by kz650guy123.

Trying to figure out the air screw 79 KZ650BE ? Need an o-ring ? 07 Sep 2023 11:12 #889140

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Warren the ptfe tape is an idea. But I would be afraid that would fall into the carb ?


No chance, there's a step from the thread to the taper. 
 

Z1000J2 somewhat modified!

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Trying to figure out the air screw 79 KZ650BE ? Need an o-ring ? 07 Sep 2023 11:47 #889142

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Ckahleer thanks for the part #. But that is only a o-ring. As I stated in the post my screw doesn't even have a groove for an o-ring.
What I need is for a replacement screw WITH an o-ring on it.
That's what I'm having trouble finding.
Are you sure there should be a grove. Any mixture screw I have worked with, the o-ring would slide on the smooth section of the screw as the screw was turned in and out. 
94 KE100
81 CM200t
82 KZ305
85 VT 500c
85 VF1100c
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Trying to figure out the air screw 79 KZ650BE ? Need an o-ring ? 07 Sep 2023 11:56 #889144

  • Nessism
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If you look at the parts fishe, such on Partzilla, you will see that there are two different air screws listed.  The standard type that takes an O-ring, and fits 650/900/1000 bikes with VM carbs, and a second PN, presumably without the O-ring groove, that's specific to the 650.  

I don't know if the port in the carb is different between the two types of carbs, which take the different screws.  If they are different, then you are stuck with the stock pilot air screws.  If they are the same, then you should be able to source the type of screws that use O-rings.  There are lots of them on eBay.  It seems to me, though, that if a wrap of teflon tape solves the air leakage problem, the fix is a nobrainer.  As long as the tape isn't loose, below the threaded area of the screw, it won't come loose and get sucked into the carb passage.  Another option is to adjust the screw where you want it, then seal over the top of the screw with a soft sealer of some type.  
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Last edit: by Nessism.

Trying to figure out the air screw 79 KZ650BE ? Need an o-ring ? 08 Sep 2023 07:55 #889164

  • kz650guy123
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Here is a picture of the carb and the air screw. Yes the carb is dirty.
As you can see there is no where to add an o-ring to this screw.
The teflon tape might work. I think I'll just use the grease for now.
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Last edit: by kz650guy123.

Trying to figure out the air screw 79 KZ650BE ? Need an o-ring ? 08 Sep 2023 08:01 #889165

  • Wookie58
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I think Nessism's suggestion of RTV etc once the screws are set is probably preferable to grease and easy enough to remove
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Trying to figure out the air screw 79 KZ650BE ? Need an o-ring ? 08 Sep 2023 08:15 #889166

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Ok thanks Wookie. I think I'll leave the grease in there until I'm sure it's tuned the way I want it.
Then I'll probably use some hi temp rtv.
thanks all

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Trying to figure out the air screw 79 KZ650BE ? Need an o-ring ? 08 Sep 2023 08:26 #889167

  • martin_csr
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Just an FYI.  At Partzilla the diagrams for the 1980 KZ650F and 81 KZ650-CSR list an air adjusting screw w o-ring and a pilot adjusting screw without o-ring, and they fit into the same orifice as the 79 models. The part numbers are the same between the models and are the same as some of the earlier 650s to 1978, although only the 80-81 650s have the screws without o-rings.  The 81 air adjusting screw w o-ring is for the Canadian models where EPA regs don't apply and the same is probably true for the 80 models.

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Last edit: by martin_csr.
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