Petcock still leaking after rebuild - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 12 (permalink) Old 09-26-2012, 06:29 PM Thread Starter
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Petcock still leaking after rebuild

I bought a Petcock kit on ebay, rebuilt my petcock and fuel is leaking out of the air filter connected to the carb (ear shave). When I disconnect the fuel line from the carb, fuel drips out directly from the petcock.

I made sure to install everything exactly how I took it apart. From what I've read, it looks like the vacuum is not working as it should. I made sure the spring is in the correct place, but it still leaks. I put pressure on the diaphram using my finger, and then tried to suck the fuel line, but didn't get any flow. I then put everything back together and when I suck on the fuel line it creates air flow. It seems like the spring is not strong enough, but it is the original spring, and I had to push pretty hard with my finger to create the vacuum.

Is the kit bad, or do you think it is something on my end?

Any help is appreciated.

Ben

1986 Vulcan 750
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post #2 of 12 (permalink) Old 09-26-2012, 07:00 PM
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Last edited by FlacoLove; 03-25-2013 at 03:01 AM.
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post #3 of 12 (permalink) Old 09-26-2012, 07:11 PM
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correct me if I am wrong..........but even if the petcock is wide open it shouldn't really matter if the carbs are functioning properly. If you are getting fuel overflow from the carb when the bike is off, it can only mean one thing.....the float is allowing fuel to enter the carbs when there is no demand.

Fix your floats and carb issue and you should be able to leave the petcock wide open all the time.
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post #4 of 12 (permalink) Old 09-26-2012, 07:39 PM
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Quote:
correct me if I am wrong
Youre wrong.. had to say it.. but here is why

Whether the floats are stuck open or not, Fuel should not reach the carbs with the petcock off, or no vacuum to the carbs. even if the fuel were to flow constantly, the float bowls will over flow if the fuel has no where to go... what happens when you leave a facet on and have a cup to catch the water.. the cup overflows... put in a float to shut close off the hose, but once the pressure between the hose and the cup equalize, water will flow again.. same concept...
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post #5 of 12 (permalink) Old 09-27-2012, 01:18 AM Thread Starter
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I unscrewed the copper vacuum fitting and a little debris fell out, but that didnt fix it.

Tonight I used 1500 grit sandpaper and lightly sanded each side where the diaphram touches, hoping to remove anything that might be limiting the diaphram from closing. Didn't make a difference.

While I sucked on the vacuum line, My son was able to easily blow the fuel line. When I stopped sucking the vacuum line, a little bit of air still flowed through the fuel line. Just enough to hear a squeak or slight sound. If I blew on the vacuum line, forcing the diaphram to shut completely, my son wasn't able to blow on the fuel line and we didn't hear anything.

It seems to me the new diaphram is not working or the spring is too weak. I'm leaning towards the diaphram since the spring is the original. The kit I bought said it fit multiple bikes, maybe I should have bought this from the dealer instead of going generic?

Any thoughts or recommendations?

Ben

1986 Vulcan 750
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post #6 of 12 (permalink) Old 09-27-2012, 01:38 AM
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Quote:
Originally Posted by bmarkley View Post
I unscrewed the copper vacuum fitting and a little debris fell out, but that didnt fix it.

Tonight I used 1500 grit sandpaper and lightly sanded each side where the diaphram touches, hoping to remove anything that might be limiting the diaphram from closing. Didn't make a difference.

While I sucked on the vacuum line, My son was able to easily blow the fuel line. When I stopped sucking the vacuum line, a little bit of air still flowed through the fuel line. Just enough to hear a squeak or slight sound. If I blew on the vacuum line, forcing the diaphram to shut completely, my son wasn't able to blow on the fuel line and we didn't hear anything.

It seems to me the new diaphram is not working or the spring is too weak. I'm leaning towards the diaphram since the spring is the original. The kit I bought said it fit multiple bikes, maybe I should have bought this from the dealer instead of going generic?

Any thoughts or recommendations?
Depending on how old that petcock is, the spring could be too weak to close the valve. Have you considered stretching the spring some? It would, at the very least, eliminate whether the spring is the culprit or not.

I only understand what I don't understand.
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post #7 of 12 (permalink) Old 09-27-2012, 01:58 AM
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Whether the floats are stuck open or not, Fuel should not reach the carbs with the petcock off, or no vacuum to the carbs.
True, but if the petcock is leaking, fuel will get to the carbs.
even if the fuel were to flow constantly, the float bowls will over flow if the fuel has no where to go...??????? If the fuel is still flowing to the carbs, the floats will shut the fuel off. That is what they are there for. To let fuel in when it is needed, and to shut the fuel off when the float bowls are full. So therefore they will NOT overflow.
what happens when you leave a facet on and have a cup to catch the water.. the cup overflows. Not the same concept. Water in a sink will overflow the cup because the water is getting past the faucet. There is nothing there to stop the flow. Gas in a tank won't get past the floats in a carb because they will shut off the flow of gas.
.. put in a float to shut close off the hose, but once the pressure between the hose and the cup equalize, water will flow again.. same concept.. True, same concept, fuel will flow once the demand is there for more fuel. Once the demand is gone, the fuel will shut off.
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post #8 of 12 (permalink) Old 09-27-2012, 02:02 AM
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You can stretch the spring in the petcock to see if it will help with the leak. Tacoma Screw or Fastenal will have a big selection of springs that might work in it's place.
I know it's a PITA to have to take the valve apart again, but replacing the spring might be your best option. Without vacuum to the petcock, there should be NO fuel getting past it.
It should take a fair amount of vacuum to get the valve open. So it does sound like the spring is getting, or is already weakened enough not to let the valve close properly.
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post #9 of 12 (permalink) Old 09-27-2012, 06:39 AM
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post #10 of 12 (permalink) Old 09-28-2012, 03:41 PM Thread Starter
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Quote:
Originally Posted by FlacoLove View Post
Perhaps you didn't understand me at post #2 above. Let me try this a different way...

When you open up the petcock (what? 4 little plilips screws?), and you now have two halves, focus on the part of the petcock that does not have that new diaphram you just installed (plastic center piece). Focus on the side of the petcock housing that has the vacuum hose fitting attached to it. THAT is where your problem lies. Within it is a real tiny spring (not included with the rebuild kit) that pushes against a tiny piece of metal that closes a port. I am certain there is some debris preventing that door from fully closing; hence: constant flow, especially if you just claimed to have removed that vacuum fitting and crap fell out.. That's the part of the housing that's dirty; filled with deposits caked up in there. Drown that part with carb cleaner and blow hard (inside/out) then give it a suction test from the fitting side until you get a good close. Forget those new parts you just installed; that's not where your problem lies. Ride safe.
I took the petcock apart again and dropped the side with the vacuum fitting into a can of chem-dip. I'll leave it over night and let you know. When taken apart, I was able to blow through the vacuum fitting without any resistence, but cleaning it can't hurt.

I'll let you know, thanks for help.

Ben

1986 Vulcan 750
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