Leaking petcock after rebuild - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 7 (permalink) Old 02-14-2018, 10:07 AM Thread Starter
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Leaking petcock after rebuild

Hey All,
In December 2016 I rebuilt my petcock and replaced the carb's air cutoff valve (this) on the left side. About 3 weeks ago we woke up to a lovely gas smell all throughout the house. After doing some inspecting I noticed it was dripping from around the same spot, the cover by the air cutoff valve right by the idle adjusting knob and had left a nice puddle on the garage floor. I was under the impression that gas should not get past the petcock without vacuum, however if I loosen the drain screw at the bottom of the carb, gas freely flows.

I haven't gotten out there yet to pull the petcock, but I did remove the air cutoff valve cover and saw rubber gasket did get a bit kinked and not seated in it's little ridge properly, but I'm thinking this wouldn't be able to cause the fuel flow issue, the problem is likely with the petcock itself again right? And then it likely got to where it was kinked and decided it was a good spot to leak out.

The bike was not driven very much due to us moving and dealing with a lot of house crap, could it just be from it sitting? I always mix a little seafoam in my gas when I fill it up and put more in when I filled it before storing for winter. When I went to move the knob on the petcock from ON to RES it did give quite a bit of resistance and kind of 'pop' before it moved.

Any suggestions of anything I should look for when I take the petcock off? Going to probably do that this evening, will keep you posted!

1985 VN700 - ~5800 miles
-Plexifairing Windshield
-Leather Saddlebags & Front fork tool bag
-Engine Guard
-NGK Iridium Plugs / NGK Plug ends / New plug wire
-AGM Battery
-Kuryakyn ISO style Grips
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post #2 of 7 (permalink) Old 02-14-2018, 11:41 AM
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May be a hole worn into the diaphragm in the petcock. When that happens you get free flow of fuel, and usually end up with gas in the oil, even with the petcock turned off.

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post #3 of 7 (permalink) Old 02-14-2018, 12:28 PM
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Also, it doesn't take a large hole to kill the petcock, and it may not be easily seen. Mine just looked like a faded worn gray area, but it still filled the crankcase overnight.

If the vacuum line to the petcock is wet with gas, it has a failed diaphragm.

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 #4 of 7 (permalink) Old 02-14-2018, 02:55 PM Thread Starter
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Havent popped off the whole thing yet but I pulled the vac hose off and the inside is totally dry. Looks like there was a bit of oil or possibly gas (doesnt have a strong gas smell though) on the tip where it was touching the body of the petcock but nothing inside. I can see that where the diaphragm meets the white plastic on the petcock is a little wet as well.Probably leaking a little gas from there.

Not sure if there's another way to tell if there's oil in the gas, everything kind of smells like gas right now so taking the top off and takin a whiff wont do it.

Will try to pull the petcock off tonight to inspect everything, no idea what couldve happened in a year.

1985 VN700 - ~5800 miles
-Plexifairing Windshield
-Leather Saddlebags & Front fork tool bag
-Engine Guard
-NGK Iridium Plugs / NGK Plug ends / New plug wire
-AGM Battery
-Kuryakyn ISO style Grips
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post #5 of 7 (permalink) Old 02-14-2018, 07:31 PM
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You can take the vac line off the petcock, turn the petcock on, and see if the vac port gets wet at all, even one drop. Should be no gas at all on the vac port.

If it's not the diaphragm, could be the o-ring is shot and is just leaking to the outside.

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 #6 of 7 (permalink) Old 02-15-2018, 09:07 AM Thread Starter
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Thanks, I'll give that a shot tonight. I drained the gas since it didn't want to stop so I'll throw some in and toss it in reserve, there's no 'OFF' on this petcock. The wife wasn't too thrilled about me wanting to wrench on the bike on valentines day so didn't mess with it yesterday

1985 VN700 - ~5800 miles
-Plexifairing Windshield
-Leather Saddlebags & Front fork tool bag
-Engine Guard
-NGK Iridium Plugs / NGK Plug ends / New plug wire
-AGM Battery
-Kuryakyn ISO style Grips
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post #7 of 7 (permalink) Old 02-16-2018, 12:34 PM Thread Starter
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Well not sure what the issue was exactly. There was a bit of crusty stuff in the petcock, so maybe the gas started to varnish a little, or maybe it was due to rusty gas drying up. There was a bunch of rusty crap in the bottom of the tank after draining, no idea where that came from. Hosed that out really good till it ran clear, WD40'd it, and rinsed it with gas.

Gas in the bottom of the tank was now clear/slightly yellowish as it should be instead of orangeish. I cleaned the petcock out of all crusty crap and put it back together, I stretched out the spring in the back behind the diaphragm a little as well, no drips so far after filling everything back up. Wish I had clear fuel lines so I could be sure, might be a project for this spring.

Looks like it was a $0 fix, hopefully it sticks.

1985 VN700 - ~5800 miles
-Plexifairing Windshield
-Leather Saddlebags & Front fork tool bag
-Engine Guard
-NGK Iridium Plugs / NGK Plug ends / New plug wire
-AGM Battery
-Kuryakyn ISO style Grips
Godfree is offline  
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