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2002 kawasaki ZX636 gas leak

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nomibzu
L Plate Warrior



Joined: 01 Jan 2020
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PostPosted: 22:38 - 01 Jan 2020    Post subject: 2002 kawasaki ZX636 gas leak Reply with quote
Hi everyone, I need some suggestions regarding this:

I noticed a lot of gas leaking from the carbs, so I took out the carbs for cleaning.The pilot jets were clogged but apart from that everything seemed to be in order. The floats were moving freely and needles were in good shape. I put the carbs back in and it is still leaking.

The leak only happens when I am riding, or when I come to a stop. It does not leak when the engine is off. I looked under the tank and I see the gas coming out of one air fuel mixture screw. I changed the o-rings in all 4 mixture screws when I cleaned the carbs yesterday. The springs and washers also looked okay. What could be the possible reasons for this?

One of these screws is leaking:
https://imgur.com/gallery/tjDNKy1
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jaffa90
World Chat Champion



Joined: 06 Apr 2016
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PostPosted: 02:08 - 02 Jan 2020    Post subject: Reply with quote
The pilot jets were clogged! Why?
It sounds like the needle valve/s are not seating and over filling.
Also fuel flow stops with bike switched off.
I suggest a carb kit and a fuel tap kit with an inline fuel filter being finer than the internal filters if possible.
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nomibzu
L Plate Warrior



Joined: 01 Jan 2020
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PostPosted: 14:06 - 02 Jan 2020    Post subject: Reply with quote
jaffa90 wrote:
The pilot jets were clogged! Why?
It sounds like the needle valve/s are not seating and over filling.
Also fuel flow stops with bike switched off.
I suggest a carb kit and a fuel tap kit with an inline fuel filter being finer than the internal filters if possible.


The bike was not used for a long time by the previous owner, there was old fuel in it when I bought it. That could have caused the gunk in the jets. I drained the old fuel and put new fuel with carb cleaner additive a few weeks back.

After this recent carb cleaning, bike starts and idles smoothly and runs perfectly. The leak is the only problem now and it is happening from only one mixture screw, the other 3 are fine.

1- You mean the fat needle inside the float body which closes the fuel supply when the floats rise OR the long needle connected to the diaphragm which goes in to the main jet ?

2- The mixture screws are working as the overflow outlet in this case? Is there also any separate mechanism for dealing with the excess fuel/overflow in the carbs as well?

* I am very new with DIY bike repair. This was the first time I opened and cleaned the carbs ever, so please excuse my noob level wording/knowledge Smile
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Easy-X
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Joined: 08 Mar 2019
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PostPosted: 14:35 - 02 Jan 2020    Post subject: Reply with quote
It'd be a bit odd for fuel to leak from the mixture screws. Petrol has a habit of creeping about from unexpected places - be sure it really is that screw.

Nice and simple on a single carb: big fat pipe for fuel in and a smaller pipe for overflow (and maybe a breather pipe as well) with linked carbs pipework gets chained together so it can be a bit harder to work out what's going where.
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Tankie
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Joined: 24 Feb 2017
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PostPosted: 16:46 - 02 Jan 2020    Post subject: Reply with quote
check the float heights first
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nomibzu
L Plate Warrior



Joined: 01 Jan 2020
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PostPosted: 12:17 - 03 Jan 2020    Post subject: Reply with quote
Tankie wrote:
check the float heights first


Yes I will take the carbs out again to check this. But is it possible that the fuel would leak from the air fuel mixture screw in case of overflow? Or is there supposed to be a separate overflow outlet ? The carb on my bike is Mikuni BDSR 37.
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Tankie
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Joined: 24 Feb 2017
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PostPosted: 12:30 - 03 Jan 2020    Post subject: Reply with quote
Don't know the specifics of your carbs, but I would say they will probably have breathers
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jaffa90
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Joined: 06 Apr 2016
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PostPosted: 14:11 - 03 Jan 2020    Post subject: Reply with quote
I would service the carbs and bench check for overflowing,
does this bike have fuel pump?
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nomibzu
L Plate Warrior



Joined: 01 Jan 2020
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PostPosted: 14:46 - 03 Jan 2020    Post subject: Reply with quote
jaffa90 wrote:
I would service the carbs and bench check for overflowing,
does this bike have fuel pump?


Yes the bike has a fuel pump.
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jaffa90
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PostPosted: 15:37 - 03 Jan 2020    Post subject: Reply with quote
I cannot help any more because i`ve never benched checked carbs under fuel pressure before fitting.
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nomibzu
L Plate Warrior



Joined: 01 Jan 2020
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PostPosted: 16:25 - 03 Jan 2020    Post subject: Reply with quote
jaffa90 wrote:
I cannot help any more because i`ve never benched checked carbs under fuel pressure before fitting.


It is okay. I am hoping float level adjustment and cleaning of the float valve seat + o-ring replacement would fix it. But can a leaking float valve cause a continuous leak or just a few drops ? Because I can see a constant drip.
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Tankie
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Joined: 24 Feb 2017
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PostPosted: 17:01 - 03 Jan 2020    Post subject: Reply with quote
If there is fuel in the system and you have a float valve fault it will run until the tank runs dry, check the levels and if a float valve is leaking replace it
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