Sudden gas leak?!?

Afan · Sep 15, 2016

I know, "sudden" sounds weird, but...
I parked my ST1100 almost a month ago, because of bad rear tire, and went to Bosnia last two weeks to visit my parents. And I JUST few minutes ago wanted to go for a short ride and the moment I turned the engine on - gas started leaking. It was more streams than drops. I smelled gas while taking the bike out of garage and then saw the wet spots. I stopped, turned the engine off, put on the side stand and found the bike is leaking gas. But it stopped when I turned the engine off. When I turned the engine on again to put the bike back into garage - it started leaking again. And I'm sure there was no leaking spots under the bike before. So, as long as it's off - no leaking.
First, how that "sudden"?
Second, what it cold be? Fuel pump? Carb? I can't work on it right now but I wold like to know what it could be.
Any help appreciated.

Oldbikefixr · Sep 15, 2016

You have a loose or broken pressure line somewhere. Or, possibly a missing float bowl drain screw.

Afan · Sep 15, 2016

This is funny! When doing research on the forum about the gas leaks, I found my own, "very similar" thread "Fuel leak when the engine is running inly" :rofl1:

Looks like the history's repeating!

Since it's was almost a year and a half ago and about 25K+ miles, can't say the job was done bad.

Afan · Sep 15, 2016

As somebody suggested on that old thread, I have to take off the plastics first and do some research - saves in time. Now is more poking hole in darkness...

dkruitz · Sep 15, 2016

When I bought mine fresh from a barn last year it had gas pouring out of the carbs. The float valves/needles were stuck, and there were pinched off fuel bowl gaskets - PO had no clue what he was doing.

Keep a fire extinguisher handy when troubleshooting, and roll it outside of the garage just-in-case it all goes up in flames. With the key on (bike not running), and the Run/Stop switch moved to Run, the fuel pump will run for about 2 seconds to prime the carbs. Do this a few times to replicate running the engine (no spark and less heat means less of a chance for fire.) You might want to do this on the center stand too. The drains on the bowls should all come together as a 4 into 1 hose assembly directly under the carbs. Use a could strong flash light to determine the high point of the leak(s). Let us know what you find and good luck!

Be sure to check your oil level to make sure you haven't filled the crankcase with gas.

And don't be afraid to jump in there - the folks here can really help even if you have no experience to speak of.

TerryS · Sep 15, 2016

My 1990 bike decided to spring a leak from one of the fuel supply hoses after the T connector where it fits onto the carburetor stub. The old hose was starting to split at the end, so I trimmed back to some better feeling rubber.

tomspear · Sep 16, 2016

dkruitz said:
When I bought mine fresh from a barn last year it had gas pouring out of the carbs. The float valves/needles were stuck, and there were pinched off fuel bowl gaskets - PO had no clue what he was doing.

Keep a fire extinguisher handy when troubleshooting, and roll it outside of the garage just-in-case it all goes up in flames. With the key on (bike not running), and the Run/Stop switch moved to Run, the fuel pump will run for about 2 seconds to prime the carbs. Do this a few times to replicate running the engine (no spark and less heat means less of a chance for fire.) You might want to do this on the center stand too. The drains on the bowls should all come together as a 4 into 1 hose assembly directly under the carbs. Use a could strong flash light to determine the high point of the leak(s). Let us know what you find and good luck!

Be sure to check your oil level to make sure you haven't filled the crankcase with gas.

And don't be afraid to jump in there - the folks here can really help even if you have no experience to speak of.

You might need one additional step to perform this test. If you still have a vacuum fuel cutoff you will have to bypass it or open it with an external vacuum source. One way I found to do this is to connect a soft vacuum line to the vacuum fitting on the backside of the valve and suck on it (mouth power is enough to open the valve). Then while maintaining suction, clamp the line with hemostats. That should keep the valve open so you can perform the "key on" leak test.

Tom
STOC 2316
Aurora, CO

dkruitz · Sep 16, 2016

You are correct, I forgot that portion since I did the vacuum valve delete procedure so quick into my ownership.

tomspear said:
You might need one additional step to perform this test. If you still have a vacuum fuel cutoff you will have to bypass it or open it with an external vacuum source. One way I found to do this is to connect a soft vacuum line to the vacuum fitting on the backside of the valve and suck on it (mouth power is enough to open the valve). Then while maintaining suction, clamp the line with hemostats. That should keep the valve open so you can perform the "key on" leak test.

Tom
STOC 2316
Aurora, CO

Jim Van · Sep 16, 2016

I bet the cause of your problem will be very obvious after you get the plastic removed and do a visual inspection.

Afan · Sep 18, 2016

Ok, this is REALLY weird. If can somebody explain it to me: friend of mine, who helped me with the bike (and eventually the same problem) first time, came to me yesterday. Before he got here I put my bike in the middle of garage pushing it left and right. And took almost all of tupperware. He came, looked with his flashlight around and asked me to turn on the bike. I put a pan under the bike and turned it on. And - nothing?!?!?!?!? Not a drop of gas! With and without choke, handful of throttle - nothing.
Went to local service to put new rear tire, the friend was following me just incase, everything was ok. Went home - no problems. Just checked again - no leak!

Not that I'm disappointed

but like to know what's going on?

Jim Van · Sep 19, 2016

Don't be too disappointed - It will start leaking again.

Afan · Sep 19, 2016

Jim Van said:
Don't be too disappointed - It will start leaking again.

HA HA HA HA HA...

Jim Van · Sep 19, 2016

I wasn't trying to be funny. A leak like that won't cure itself. Please let us know if it starts again and what the problem turns out to be.

Afan · Sep 19, 2016

Jim Van said:
I wasn't trying to be funny. A leak like that won't cure itself. Please let us know if it starts again and what the problem turns out to be.

I know. And I know it could/will happen again. It's just we didn't know what to fix because can't see anything, can't follow any trail... Eventually we could (should?) disassemble and clean the carburetor, but since no more trouble I was trying to replace my tire.

I wish I can do some extra maintenance over Winter but my garage is damn cold!

Afan · Jan 23, 2017

Jim Van said:
I wasn't trying to be funny. A leak like that won't cure itself. Please let us know if it starts again and what the problem turns out to be.

And, as you assumed, it happened again.
So, the bike was sitting from September 'til November fixing my final drive problem. It was fixed and when I test the bike, just down the road, it started to spilling gas. Again. :banghead:
Then came Holidays. Then had to fly to Europe for dad's funeral,...
Yesterday I decided it's time to work on the bike again and try to figure out what's going on. Friend of mine came to my house with his trailer to tow the bike to his garage. While I was waiting for him I took the bike outside of my garage and, out if curiosity I started the bike. And, guess what? No spills. Everything's ok. The same like last time when it was spilling and then, as you said "cured itself". We took the bike to his garage anyway to try to figure out why is this happening but without trails we didn't do much.
And I have to "fix" it before my 2-week trip to California.

Ideas?

Afan · Jan 23, 2017

Even the carburetor was cleaned thoroughly a year ago, I still think it i causing the problems. Maybe one of the floats gets stuck and then gets "un-stuck" somehow...?

Brant · Jan 27, 2017

Afan, just a guess, but suspicious that the safety fuel shut-off diaphragm is leaking internally, then to the outside of it

.

Uncle Phil · Jan 27, 2017

My bet would be on a carb float that 'sticks' open then unsticks itself. Or could be a piece of trash stuck in the mechanism somewhere. IIRC, the ST1100 floats are hollow. See if one of them is pinholed (fills up with gas in use then empties while sitting). Just some guesses.

Afan · Mar 14, 2017

Finally yesterday I was able to continue to work on my bike. Plan was to take the carbs off of the bike. Before I pull the cards off I peaked with flashlight under the carbs and found that one of the float bowl drain hoses (I hope I use correct terminology) wasn't attached to to the bowl at all. And when I pulled the carbs other three disconnected soooo easy, like they were barely attached?!? And they are in pretty bad shape. So, I think (and hope) that's what was causing the gas leak. Since it has coolant leak and clutch slave cylinder leak too, I'm building the list of parts I have to order. Almost thinking to change the name of my bike to "Swiss cheese".

:

So, just to be sure, here is the picture of the drain hoses I want to replace

and, according to carburetor assy fiche

it's items 32, 2 x 37, 2 x 39, and eventually 55, right? Or I'm missing something?

The "boots" are replaced about year ago, and I already bought Thermostat L & R hoses.

Bush · Mar 14, 2017

Hey Afan. Stuff some clean rags into those intake ports before you drop something in there!

Sudden gas leak?!?

Afan

... and this is my real name.

Oldbikefixr

Afan

... and this is my real name.

Afan

... and this is my real name.

dkruitz

TerryS

tomspear

dkruitz

Jim Van

Afan

... and this is my real name.

Jim Van

Afan

... and this is my real name.

Jim Van

Afan

... and this is my real name.

Afan

... and this is my real name.

Afan

... and this is my real name.

Brant

Uncle Phil

Afan

... and this is my real name.

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