Fuel overflow after reinstalling carbs - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 22 (permalink) Old 10-19-2015, 12:36 AM Thread Starter
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Fuel overflow after reinstalling carbs

The carburetor assembly has been torn down piece by piece and cleaned thoroughly. During this process, I verified that the float assemblies were working properly (when the float drops, I cannot blow through the fuel input port at all on either carb). As far as I could tell at the time, everything on the carburetor assembly was working properly when reassembled.

In the middle of all this, I also installed coasters and pods. The two center ports come to a T and then proceed to the front right breather filter. The outer ports each connect to the petcock fuel ports. Left side carb vacuum port is connected to the petcock vacuum port. Right side carb vacuum port is capped.

When I open the petcock, the carburetors fill all the way to the air filters and begin to overflow. Any idea what I'm missing that could be causing this? I removed the carburetor rack and re-verified that the float assembly was working by blowing into the fuel input hose while tilting the assembly. Both worked as designed. On reinstall, the overflow happened again.

Suggestions are greatly appreciated. Thanks!

1986 VN750 27k miles
1999 EN500 32k
1983 GL650i in pieces. Someday it will ride again.
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post #2 of 22 (permalink) Old 10-19-2015, 07:47 AM
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Just about has to be the floats sticking, needle valves stuck open. Or float height too high, not likely in both carbs.

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post #3 of 22 (permalink) Old 10-19-2015, 08:28 AM Thread Starter
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I agree that float valves sticking would cause this, but why do they stop airflow when the carb assembly is tilted off the bike? Also, float valves sticking wouldn't likely present itself on both sides simultaneously, just like incorrect float height.

Not trying to argue, just wrapping my head around the symptoms.

1986 VN750 27k miles
1999 EN500 32k
1983 GL650i in pieces. Someday it will ride again.
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post #4 of 22 (permalink) Old 10-19-2015, 08:42 AM
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Just can't think of any other way for the carbs to overflow like that. Some way, the needle valve isn't shutting off gas flow. I can't explain not being able to blow though, that's really strange to have both.

Floats aligned, installed correctly, not rubbing ? Needle valve still clipped onto the float?

After more reading .... The petcock shouldn't flow fuel until vacuum is applied, as in cranking or starting the engine. (edit: 1986 model? You probably have the 'Prime' setting on that year petcock. In that case, fuel flow there is normal.)

It's possible for the front carb to get extra fuel if the petcock leaks through the vacuum port, but not both carbs.

2003-21k mi
Shaved w/UniPK92+Stock Jets-TPE/MOSFET-Shinko Tires-AGM batt-bags-chrome-LEDs...more
__________________________________________________ ____________
Repair Manual: http://www.mediafire.com/file/mj7z81..._Catalogue.pdf

Owner's Manual: http://www.mediafire.com/file/nscb5f...ers+Manual.pdf

Last edited by Spockster; 10-19-2015 at 08:51 AM.
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post #5 of 22 (permalink) Old 10-19-2015, 08:45 AM
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Don't have the vent ports on the carbs mixed up with the fuel inlet?

In that scenario the fuel flows into the vent non-stop... then the full carb is shut off at the float, giving you overflow and no-blow.

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__________________________________________________ ____________
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post #6 of 22 (permalink) Old 10-19-2015, 09:20 AM
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Quote:
Originally Posted by Spockster View Post
Don't have the vent ports on the carbs mixed up with the fuel inlet?

In that scenario the fuel flows into the vent non-stop... then the full carb is shut off at the float, giving you overflow and no-blow.
Been there...

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post #7 of 22 (permalink) Old 10-19-2015, 09:22 AM Thread Starter
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Vents reversed with fuel inlet would definitely be the simplest explanation. I've attached a carb picture stolen from eBay...
The two outer hoses in the picture are connected to the fuel outlets on the sides of the petcock.
The plastic hose connection in the center that joins two hoses going to the carburetors is routed to the breather at the front right of the frame roughly where the factory filter ear was.

And yes - it's an '86 petcock with a Prime position.
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1986 VN750 27k miles
1999 EN500 32k
1983 GL650i in pieces. Someday it will ride again.
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post #8 of 22 (permalink) Old 10-19-2015, 12:41 PM
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Quote:
Originally Posted by calebj View Post
Vents reversed with fuel inlet would definitely be the simplest explanation. I've attached a carb picture stolen from eBay...
The two outer hoses in the picture are connected to the fuel outlets on the sides of the petcock.
The plastic hose connection in the center that joins two hoses going to the carburetors is routed to the breather at the front right of the frame roughly where the factory filter ear was.

And yes - it's an '86 petcock with a Prime position.
It's hooked up correctly.

I would have to go back into the carbs and check out the floats/needles.

. But having overflow without being able to blow through???? Is there so much gas, maybe you can't blow it through the hose? When you do the blowback method to unplug a carb, there's quite bit of resistance because you are only forcing gas through the jets, emul. tube, and the needle valve.

You'll need to check your oil for gas too.

2003-21k mi
Shaved w/UniPK92+Stock Jets-TPE/MOSFET-Shinko Tires-AGM batt-bags-chrome-LEDs...more
__________________________________________________ ____________
Repair Manual: http://www.mediafire.com/file/mj7z81..._Catalogue.pdf

Owner's Manual: http://www.mediafire.com/file/nscb5f...ers+Manual.pdf
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post #9 of 22 (permalink) Old 10-19-2015, 12:47 PM Thread Starter
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That's just it - I can blow through each fuel line until I rotate the carb enough for the respective float to move.

Guess I'll just tear the carbs out again and open them up. I'll take a few pictures as I go and post them in case something stands out. I'm sure there's an ID10T error in here somewhere...

Once it's resolved, I'll definitely change the oil. Need to do that to pull and rebuild the starter anyway.

Thanks for all your help.

1986 VN750 27k miles
1999 EN500 32k
1983 GL650i in pieces. Someday it will ride again.
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post #10 of 22 (permalink) Old 10-19-2015, 01:33 PM
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Maybe need to adjust float bowl height.bowls might leak...

ONE RATS ASS GIVEN PER POST
Support your local FREEBIRDS MC
1986/5 Vn700/750 Frankenfook cross eyed bitch "Mellisa Fayhe"
I am a BIKER and i'm proud.FREEBIRDS MC CENTRAL NY

lowered with progessive 412 10" shocks
rejetted for K/N Pods part#rc 2340
sportster seat

'I didn't lose my mind.i gave it away

BRING BACK WOLFIE."Peace and Carrots"RIP
"And I'm free...as a bird"John Lennon Free as a Bird
"I only carry when I have my pants on"Joe Robinson RIP aka Old Dog
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