Fuel problem - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
Carbs and Fuel System
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post #1 of 14 (permalink) Old 12-15-2011, 02:23 PM Thread Starter
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Fuel problem

Went out to my bike to find the floor stained with gas. It's been raining, so the gas puddle is gone but there's the stain still there and the smell.

Also, my tank is now empty u_u I let the bike sit since Tuesday. I hadn't gone out to it since then and now this is what I found.

So I'm guessing my carbs need to get kicked out again. I think the petcock is working right, I rebuilt it a few months ago and I haven't seen it leak since then. Can't really test it right now since I have no fuel in the tank u_u

So what should I concentrate on? Floats and needles?

Anyone wanna give me a set of good working carbs for Christmas? lol

My damn "new" hockey puck is also acting up... I don't seem to have good luck with those lol but that goes on another topic altogether.
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post #2 of 14 (permalink) Old 12-15-2011, 03:46 PM
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I'll bet it is still your petcock. I rebuilt mine and it decided to leak on me again.

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post #3 of 14 (permalink) Old 12-15-2011, 04:29 PM Thread Starter
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Well, the leaking appeared to be from the carbs rather than the petcock, judging by the fuel drops that I found around the carbs... Still, I will definitely test the petcock once I get some gas in the tank. Don't have a car right now to go get gas :-/ so it will have to wait a bit.
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post #4 of 14 (permalink) Old 12-15-2011, 05:00 PM
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I know I've read several posts about the floats sticking alowing the fuel to flood the carb & leak out. Without a tear down, you could always try the great "Sea Foam", if it's available to you.

Either way, it shouldn't be anything to major. You can get to the float bowls easy enough & check them to see if they're stuck!
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post #5 of 14 (permalink) Old 12-15-2011, 06:42 PM
If only it had 6th gear..
 
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I would agree about the petcock except going back to what I know about carbs, but taking into account that these are different for sure, the float needle valves are to my knowledge solely responsible for regulating the fuel in the carbs at any given time. The petcock is only on or off so when the bike is running and producing vacuum, gas flows until the floats are satisfied and then flow is stopped to prevent flooding (provided that your PC diaphragm is in tact). The PC is still open at this time though -the needle valve has stopped the flow. I fully admit that I could be missing something that happens when the bike is sitting but, when you look at the design of each carb individually, you have a gas line that feeds directly to the float valve. There is no other feed so, theoretically you should be able to put your valve on "PRI" (on older bikes of course) and there should no leak if the floats are working properly.

I missed something There is the possibility of the diaphragm having a tear or pinhole in it but that should only allow gas to enter through the vacuum port while the engine is running not sitting. This could be easily checked by plugging or pinching the vacuum line to the petcock while it sits for a while to see if it still leaks. Or if you have a vac pump you could use it to see if it pulls gas from the petcock vac line.
I love to learn more about these bikes, so let me know if I haven't got it right or missed something.

And Ceal, sorry you're having troubles still with the stuff you've already replaced. Very frustrating. Good luck.

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Mods:
Jetted, shaved & coastered
Home made under-tank single filter
Converted ACCT's to manual (thanks wib714)
Dual vac lines on petcock (my cure for ticking)
LED tail/plate lights
Relocated helmet lock to license plate

Added stuff:
Customized hard bags w/ lights
Chrome levers
Hellcat windscreen
LED running lights
Home made 'Vita-Volt' meter
Foot rests on engine guard
Tunes

Hmm....she was on the back when we left.... ??

Last edited by DavesVulster; 12-15-2011 at 06:52 PM.
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post #6 of 14 (permalink) Old 12-15-2011, 06:43 PM
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If the petcock was operating properly, it shouldn't have allowed gas to get to the carbs with the bike off. Not sayin' the carbs aren't defective too, but the petcock definitely is.

I'm keepin' all the left over parts. I'm gonna use 'em to build another bike!
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post #7 of 14 (permalink) Old 12-15-2011, 07:24 PM Thread Starter
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hmm good points here... definitely need to take a good look at everything.

I didn't see the petcock leak before, but this time I think I left it on the "res" position, maybe that position isn't working as it should and the "on" was working right... I dunno, I'll update when I can check the petcock.
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post #8 of 14 (permalink) Old 12-15-2011, 09:06 PM
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If it hasn't been modified from stock, the petcock shouldn't freely flow gas except in the Prime position.

I'm keepin' all the left over parts. I'm gonna use 'em to build another bike!
_____________________________________________
"Black Beauty"
1989 VN750 acquired December, 2008, 6,711 miles
Currently 23,298 miles

Old Blue
2001 Honda CMX250 Rebel acquired July, 2008

1987 VN750 project bike, acquired August, 2009, 33,000 miles and balancer sticking out of the case, currently awaiting attention and parts
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post #9 of 14 (permalink) Old 12-15-2011, 09:39 PM
If only it had 6th gear..
 
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Quote:
Originally Posted by flitecontrol View Post
If the petcock was operating properly, it shouldn't have allowed gas to get to the carbs with the bike off. Not sayin' the carbs aren't defective too, but the petcock definitely is.
Right. Like if it doesn't fully close and lets gas seep when the bike is off.

Lets say the floats are ok. Do you think if the diaphragm had a hole in it and the valve never fully closes, gas could seep into the carbs thru the vac port by gravity? Just thinkin about stuff...

Dave

Mods:
Jetted, shaved & coastered
Home made under-tank single filter
Converted ACCT's to manual (thanks wib714)
Dual vac lines on petcock (my cure for ticking)
LED tail/plate lights
Relocated helmet lock to license plate

Added stuff:
Customized hard bags w/ lights
Chrome levers
Hellcat windscreen
LED running lights
Home made 'Vita-Volt' meter
Foot rests on engine guard
Tunes

Hmm....she was on the back when we left.... ??
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post #10 of 14 (permalink) Old 12-15-2011, 10:36 PM
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Quote:
Originally Posted by DavesVulster View Post
Right. Like if it doesn't fully close and lets gas seep when the bike is off.

Lets say the floats are ok. Do you think if the diaphragm had a hole in it and the valve never fully closes, gas could seep into the carbs thru the vac port by gravity? Just thinkin about stuff...
I would say it is definitely a possibility ,and there could be some crud holding it open also.But definitley the petcock needs looked at ,I wonder does this petcock have pri,position or is it on, off and reserve,as FC said if it says pri instead of res it will allow fuel through it without the bike running.Either way, it is a good reason for turning your petcock to the off position especially when parking for the day.




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