Gas Leak Problem...Again... - Sportbikes.net
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post #1 of 19 (permalink) Old 09-20-2005, 03:29 PM Thread Starter
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Gas Leak Problem...Again...

Hey everyone. I have a 1986 Yamaha YX-600 Radian. About 3 weeks ago I came out one morning and the bike had leaked all the gas left in it's tank all over the floor of my garage. When I tried to start it, it would turn over for a second or so then just totally stop. I then primed the carbs and switched to reserve (per the manual) and the bike started. I went and filled up with gas, and didn't seem to have any noticeable leaks, so I went on my business.

Since then I've had the problem 2 more times. Each time, it's the same symptoms. The thing I've noticed though, is that it doesn't seem to do it whenever the tank is more than half full. If it's got more than half a tank, it will never do it. But it seems that as soon as it gets down below half a tank, the next morning I come out to a puddle of gas. Could this be something to do with air pressure getting built up inside the tank whenever the gas level is low?? Or should I just try cleaning my carbs out and hope that makes the problem go away. I have a friend that works on bikes for a hobby/self employment and he said that he has cleaned carbs and rebuilt them for many older Yamahas, and would probably do the work for me for fairly cheap. But if anyone has any other ideas that could be the cause, I'm up for suggestions.

For what it's worth, I noticed a small amount of liquid around the gasket for the valve cover...but I've always noticed that, and only recently had the problem with the gas...so I think that they are seperate and unrelated.

Thanks.
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post #2 of 19 (permalink) Old 09-20-2005, 03:34 PM
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check all your fuel lines. I am thinking the problem might be with a dry rotted line or a cracked one

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post #3 of 19 (permalink) Old 09-20-2005, 04:05 PM Thread Starter
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Just got done doing that. There's no issue with the fuel vent (??) line...and the lines that run to the bank of carbs seem to be fine. They don't have any fuel on them at all.

The switch to select Reserve or Main also doesn't seem to have any gas leaking out of it.

As I look at it more, I'm beginning to wonder if it does have something to do with the liquid that's coming out of the valve cover. As you look at that valve cover, you can see where the "angle" of the liquid flows down to that side...which makes sense because the bike sits on it's side stand...but how the heck would gas be leaking out of the valve cover??
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post #4 of 19 (permalink) Old 09-20-2005, 04:06 PM
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Quote:
Originally Posted by DoppelgangerONE
Just got done doing that. There's no issue with the fuel vent (??) line...and the lines that run to the bank of carbs seem to be fine. They don't have any fuel on them at all.

The switch to select Reserve or Main also doesn't seem to have any gas leaking out of it.

As I look at it more, I'm beginning to wonder if it does have something to do with the liquid that's coming out of the valve cover. As you look at that valve cover, you can see where the "angle" of the liquid flows down to that side...which makes sense because the bike sits on it's side stand...but how the heck would gas be leaking out of the valve cover??

Not sure on that one either. Maybe the carb is leaking?

William (Will) SBN
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post #5 of 19 (permalink) Old 09-20-2005, 04:10 PM Thread Starter
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I also just checked the spark plugs, and they seem to be showing me that the bike is running fairly rich. I'm beginning to wonder if I have a bit of a problem with a float height...or maybe something stuck inside one of the needles??
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post #6 of 19 (permalink) Old 09-20-2005, 04:12 PM Thread Starter
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Quote:
Originally Posted by OFFICER737
Not sure on that one either. Maybe the carb is leaking?

That's what I was thinking when it first happened...but why would it only do it when it's relatively low on gas in the tank?? It seems like if there were a problem with a needle or something, that it would do it all the time, no matter how much gas is in the tank...
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post #7 of 19 (permalink) Old 09-20-2005, 04:13 PM
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maybe it is flowing into the exhaust and then leaking out? I am guessing bro becasue I haven't anything like this happen on any of my stuff, just trying to nail down anything that is inline with the fuel system

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post #8 of 19 (permalink) Old 09-20-2005, 04:14 PM
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does your engine pull from 2 different hoses...one main and one reserve or ar they both the same hose?

William (Will) SBN
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post #9 of 19 (permalink) Old 09-20-2005, 04:20 PM Thread Starter
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Quote:
Originally Posted by OFFICER737
does your engine pull from 2 different hoses...one main and one reserve or ar they both the same hose?

There are two different hoses. The problem is, the thing has 3 different settings...Main, Reserve, and Prime. Prime is only used when the bike has run out of gas (to prime the carbs)...so I'm not sure if the tubes are for reserve and main, or if the tubes are for reserve/main and prime.
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post #10 of 19 (permalink) Old 09-20-2005, 04:22 PM Thread Starter
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Quote:
Originally Posted by OFFICER737
maybe it is flowing into the exhaust and then leaking out? I am guessing bro becasue I haven't anything like this happen on any of my stuff, just trying to nail down anything that is inline with the fuel system

It's cool man...all the help I can get is appreciated...the gas is leaking out of that valve cover on the exhaust side, for what it's worth. I just seriously don't get why it only does it when the tank is half full. It's gotta be some kind of pressure or vacuum problem. I think...
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post #11 of 19 (permalink) Old 09-20-2005, 04:24 PM
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hmmm....wonder if maybe the vent hose isn't venting? it is building pressure in the tank and actually forcing the fuel out? With there being less gas in the tank it would leave more room for pressure to build up.

William (Will) SBN
R.I.P. Krazy Hawaiian-you will be missed brother!!

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post #12 of 19 (permalink) Old 09-20-2005, 04:31 PM Thread Starter
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Quote:
Originally Posted by OFFICER737
hmmm....wonder if maybe the vent hose isn't venting? it is building pressure in the tank and actually forcing the fuel out? With there being less gas in the tank it would leave more room for pressure to build up.

Yah, that's probably it. With more air in there, the pressure builds up more, which forces the gas down into the carbs. Once it's in the carbs, it has nowhere to go but into the engine...which is why it's leaking out of the valve cover.

Does that seem to make sense??

I guess a quick fix would be to just leave my gas cap open at night. At least until I can get the tube unclogged.
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post #13 of 19 (permalink) Old 09-20-2005, 04:35 PM
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Quote:
Originally Posted by DoppelgangerONE
Yah, that's probably it. With more air in there, the pressure builds up more, which forces the gas down into the carbs. Once it's in the carbs, it has nowhere to go but into the engine...which is why it's leaking out of the valve cover.

Does that seem to make sense??

I guess a quick fix would be to just leave my gas cap open at night. At least until I can get the tube unclogged.

It does to me bro....my old KX250 did it once, the only thing that made me think about it...I had forgotten about that. Make sure to lay something loose over the gas cap to make sure nothing gets in there too bro....you probably already thought about that but threw it in there

William (Will) SBN
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post #14 of 19 (permalink) Old 09-20-2005, 07:46 PM
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You have a vacuum petcock on your fuel tank. One line is going to be vacuum and the other will be the fuel line for your Prime, Reserve and On settings. Prime merely holds the petcock open without the assistance of vacuum. Reserve and On will always be "off" when there is no vacuum present. More often then not, the vacuum diapraghm gives out and the petcock stays open, like it's in PRIME all the time. This really isn't an issue if your float valves are operating properly, however if you have fuel leaks every where and they aren't coming from the tank or the fuel lines, or vacuum line for that matter, then they are indeed overflowing from the carburetor.

Check your float valves and make sure they aren't pitted, or grooved. Also, check the seats for scoring and such.

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post #15 of 19 (permalink) Old 09-20-2005, 08:35 PM Thread Starter
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Quote:
Originally Posted by Redstar11
You have a vacuum petcock on your fuel tank. One line is going to be vacuum and the other will be the fuel line for your Prime, Reserve and On settings. Prime merely holds the petcock open without the assistance of vacuum. Reserve and On will always be "off" when there is no vacuum present. More often then not, the vacuum diapraghm gives out and the petcock stays open, like it's in PRIME all the time. This really isn't an issue if your float valves are operating properly, however if you have fuel leaks every where and they aren't coming from the tank or the fuel lines, or vacuum line for that matter, then they are indeed overflowing from the carburetor.

Check your float valves and make sure they aren't pitted, or grooved. Also, check the seats for scoring and such.

So, let me get this straight...even if the thing stays in a "prime" like position (as you are suggesting could be the case with the vacuum dipraghm giving out), as long as my float valves are set properly and in good condition, I shouldn't have to worry about the overflow??

Sorry if I seem a bit slow...I don't know alot about carbs...
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