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Gas leak. Petcock?

Started by williamruck, June 17, 2008, 06:04:42 PM

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williamruck

Hey guys, I have a new quandary. Today I got back from a little trip on the Vision, and when I pulled into the parking lot I noticed I was leaving a trail of fluid behind me. When I looked closer I realized it was gas. I was leaking gas out of the carb bowl drain valve. I check to see if the drain screw had come loose, but it was nice and tight. If my petcock were stuck in the "prime" position would that do it? When I was getting the bike back up and running I didn't rebuild the petcock, do you think that might be it? What else could cause this?

inanecathode

It shouldnt do it on prime, the float should stop the gas flow. The drain isnt for carb overflow i'm pretty sure, the only circuit its drilled to is the drain screw. Your screw might not be seating right, or the oring might be bad. I'd drain the carbs and have a look at the screw and the seat inside the carb, check your o-ring too, a bad o-ring can cause a leak.
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h2olawyer

Actually, if your petcock is set to prime, it can leak out the overflow.  The fuel leaks past the needle & seat, overfilling the float bowl.  Then as the level rises, it starts draining into the overflow tube & coming out the overflow / drain tubes.

The Prime setting on the petcock allows for constant fuel flow.  If the fuel does not drain out the overflow, it will fill the crankcase with fuel.

BEFORE YOU START THE BIKE AGAIN, CHECK THE OIL LEVEL!!!  If it is now overfull, you have fuel in the crankcase & this is a potentially dangerous situation.

Rebuild your petcock as soon as possible - or install a second inline fuel shutoff.  Sounds like you could use a cleaning of the needles & seats as well.  While the needle / seat should stop the fuel flow, there is no guarantee it will - as you have found out.  You need a functioning fuel shutoff to keep the bike safe & to stop wasting the liquid gold.

H2O
If you have an accident on a motorcycle, it's always your fault. Tough call, but it has to be that way. You're in the right, and dead -on a bike. The principle is not to have any accident. If you're involved in an an accident, it's because you did not anticipate. Then, by default, you failed.

Lucky

I have found that there can be as much as 3mm variance in the length of the overflow tube in the carb, so i always set the max float hight 3 mm lower than specs.

you'll only end up with a crankcase full of fuel if you block off the drain hose with a leak situation.

when i first had my bike & didn't know any better, i blocked off my leaking drains & went inside.  the next morning i went out & started the bike, blowing fuel out the exhaust for 25 -30 feet behind me! (an exhaust valve was open)

i'm lucky i didn't grenade my bike & myself...

but boy was my crankcase clean!!!!   ;D
1982/3 XZ550 Touring Vison, Gold on Black

thisandthat

I had the same problem with my petcock leaking, although I think I've got it fixed now. I'm a bit worried that gas got in my oil, is there a way to check that? Will the gas float on top of it?

jasonm.

H2O ...you are wrong. Cathode is correct. I run mine on prime all the time.....The needle and seat stop the flow of fuel which are governed by the float. A bad float, needle/seat will cause a constant run of fuel out the overflow/drain hose. The overflow and drain use the same hose.  I get a dribble out mine from time to time. Especially when hitting the brakes hard. I think I have one of those carbs w/short overflow tube as Lucky has mentioned before.
looks aren't important, if she lets you play by your rules

h2olawyer

If I am wrong, then why did my crankcase fill with fuel once when I left it on prime?  The drains are not blocked - I've used them before & after the incident.

H2O
If you have an accident on a motorcycle, it's always your fault. Tough call, but it has to be that way. You're in the right, and dead -on a bike. The principle is not to have any accident. If you're involved in an an accident, it's because you did not anticipate. Then, by default, you failed.

Lucky

the overflow tube is connected to the drain hose & i can prove it:

blow in the drain hose & you will hear air comming out of the vent at the top rear of the carb.

the passage runs fom the top of the drain tube, thru the body of the carb & out the plastic drain fitting. the drain screw is tapped into this passage at the floor of the carb bowls. open the drain screw with the petcock on prime & you can empty the tank!

H2O, if your crankcase filled, then at least one of your drain tubes had to be blocked somehow, perhaps without you knowing it...???

--Lucky
1982/3 XZ550 Touring Vison, Gold on Black

h2olawyer

The blocked overflow is what I'm thinking.  Sure had a crankcase full of oil / gas mix, though.  Happened during the winter of 2006 / 2007.  Never even turned it over as I changed the oil before running it in the Spring.  Haven't torn into those carbs yet, to see what issues they have.  Sure sounds like there are several, though.

H2O
If you have an accident on a motorcycle, it's always your fault. Tough call, but it has to be that way. You're in the right, and dead -on a bike. The principle is not to have any accident. If you're involved in an an accident, it's because you did not anticipate. Then, by default, you failed.

inanecathode

Ugh, i must have caught something from this thread. My bike now leaves a little puddle of gas from the drain tube after parking it overnight with the petcock in the normal on position.
Solutions? Rebuild?
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If you can't tell your friend to kiss your ass then they aren't a true friend.
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Brian Moffet

Your petcock isn't sealing properly.  Either that or it is, and your carb float level is just a tad too high and when your running it takes care of itself.  Try pulling the fuel line at the petcock with it in the on position and see if the petcock leaks.  It shouldn't because there should be no vacuum to allow fuel to flow.  If you think that vacuum line got blocked so it has a permanent vacuum, remove it too to test that.

Brian

inanecathode

Word, sounds easy enough.
Off to work!
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If you can't tell your friend to kiss your ass then they aren't a true friend.
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Lucky

The petcock rebuild kit that Sirrus/Keyster sells has a lighter spring, it's akin to leaving the old one in.

the o-ring in the diaphram is what seals/shuts off fuel flow.
--be sure the diaphram doesn't have a hole
--make sure the diaphram hasn't stiffened up with years of use.
--be sure the o-ring fits tight on the diaphram button& is in good shape (not hard either)
--make sure the 'seat' area in the petcock body the o-ring seals against is clean & smooth, no pits, scratches, etc.
--make sure the spring is strong, i've been known to strech them out a bit.

meet all these conditions & the petcok won't leak.

--Lucky
1982/3 XZ550 Touring Vison, Gold on Black

williamruck

Sorry for not coming back to this but soon after I posted I went back to try and figure everything out and was able to solve the problem. I discovered that the carbs were sitting too low in their seats and when you opened up the throttle the little bar that runs between the carbs would get stuck on one of the bolts at the base of the carb seat. Essentially it wasn't letting the throttle close all the way. It was constantly giving me a wee bit of throttle! I figure that when I shut the bike down it was still holding the throttle open and would flood the carbs. I just did a little wiggling and there we go, problem solved. Now, I still have to sync the carbs, but I have been doing a lot of reading on the forum here and I think I can handle it pretty easily.

Rick G

Theres a lot to be said for QBS suggestion to install a manual fuel shut off valve in the line , after the automatic one.
Rick G
Go soothingly on the grease mud, as there in lurks the skid demon
'82.5 Yamaha XZ550 RJ  Vision,
'90 Suzuki VX800, 1990 Suzuki DR350.
'74  XL350   Honda , 77 XL350 Honda, 78 XL350 Honda, '82 XT 200 Yamaha, '67 Yamaha YG1TK, 80cc trail bike

supervision

 Mine would show wetness around the valve, so it kitted it.  Didn't fix the problem, which turned out to be seepage in the pressed in fitting.  JB weld to the rescue, cured it.
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thisandthat

My petcock leaks gas no matter what position and no matter if the vacuum hose is on off or my finger is blocking it.
If I'm right
On - Gas it let through no matter what
Primary - Gas it let through when there is a vacuum
Reserve - Same deal just takes gas from a lower point in the tank

So as far as rebuilding it goes what do I need
Theres the rubber valve, the rubber thing with holes in it, the O ring and then they vacuum thing on the far side. I think the rebuild kit has all three, do they all need to be replaced? If so are the rebuild kits generic? Or is one better then the others?

Thanks

Lucky

ON & RESERVE should flow only with vacuume, PRIME (not primary) should flow free all the time vacuume or not. prime is to refill the bowls when the bike has sat a few days or longer
1982/3 XZ550 Touring Vison, Gold on Black

Night Vision

Quote from: supervision on July 02, 2008, 11:27:41 PM
Mine would show wetness around the valve, so it kitted it.  Didn't fix the problem, which turned out to be seepage in the pressed in fitting.  JB weld to the rescue, cured it.

I experienced the loose pressed in fitting syndrome also. Everytime you wiggle/tug/pull/ the fuel line off the petcock, you chance loosening it up.

now I have a piece of fuel line before my in line shutoff so I disconnect the fuel line at the shutoff and not the petcock
if it ain't worth doing it the hard way....
it ain't worth doing it at all - Man Law
;D


if it ain't broke..... take it apart and find out why


don't give up.... don't ever give up - Jimmy Valvano

jasonm.

Quote from: supervision on July 02, 2008, 11:27:41 PM
Mine would show wetness around the valve, so it kitted it.  Didn't fix the problem, which turned out to be seepage in the pressed in fitting.  JB weld to the rescue, cured it.
I also on my '83 had the pressed fitting loosen. ALSO used JB weld Qwik. I think we have found a common issue.
looks aren't important, if she lets you play by your rules