Fuel leak from plenum (#3 Carb?)


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echinus1988
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Fuel leak from plenum (#3 Carb?)

Postby echinus1988 » Fri Feb 13, 2015 3:31 pm



Hi Everyone,

I have a 1980 Goldwing GL 1100. Bought it after it had been sitting a while, fixed it, rebuilt carbs and have been riding and enjoying fro about 6,000 miles.

Pulled it out the other day since it was beautiful and went riding. Intermittently I have been having problems with a gas leak. It appears to be coming from Carb #3.

While riding, I lost power, talking to my son on the headset, told him what was happening and he said, sounds like fuel starvation. Well, I didn't think so but out of the mouth of babes comes wisdom. I coasted over, saw a small leak at the fuel intake to the pump and figured it must be coming from there. the bike started and I continued. I got home with 62 miles and 1/4 tank! It was nearly full when I left.

I started the bike and sure enough, the leak was happening from under the carbs again. I cannot totally identify the source. It appears to come from the #3 carb, flow into the plenum and leak out from there. It doesn't make sense to me.

I have pulled the carbs and rechecked the float needle previously, it appears to be moving properly and not sticking. I have not pulled carbs yet this time. This time, I have tapped on the side of all carbs while running trying to jar any of them loose and stop it. I have yet to adjust slow speed idle jets or resync carbs. That's tomorrow unless someone gives me a better idea. I'm totally confused.

It has happened in the past but it always has stopped on its own. This time it appears it is here to stay.

As always I appreciate the time anyone takes to think about this problem and make suggestions.

Thanks.
Steve



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Johnyy Smoke
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Re: Fuel leak from plenum (#3 Carb?)

Postby Johnyy Smoke » Fri Feb 13, 2015 4:53 pm

Clean the vents in the gas cap, this can cause a vacuum in the fuel system, and can screw up the carbs. Long shot- but maybe. Regards, Johnny

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Re: Fuel leak from plenum (#3 Carb?)

Postby f1xrupr » Fri Feb 13, 2015 7:48 pm

That bike should get 40-plus mpg, but we don't know how much fuel "almost full" etc is.
It sounds like #3 carb is flooding (maybe float level incorrect), plenumn seals need replaced (gas leaking), and, sucking air at fuel pump intake (starving for fuel at road speed). Carb float levels (gas levels in carbs) are critical! It can starve for fuel just a tiny bit, and cut out. #3 carb is where the feed line enters the system-dumping fuel there, along with fuel pump sucking air could starve the other carbs.
My exercise bike is a goldwing.

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Re: Fuel leak from plenum (#3 Carb?)

Postby RBGERSON » Sat Feb 14, 2015 7:47 am

possible leaks; carb to plenum at each carb, plenum main gasket, accelerator pump o ring, bowl gasket, fuel pump, fuel lines..if the float(s) is stuck or set wrong..gas can "leak" up through the jet and flood into the plenum and down into the intake(s)..cylinders.
HAD LOTS OF GOLDWING 75-83
NOW INTO 1500'S..RIDING A 1998 SE

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Re: Fuel leak from plenum (#3 Carb?)

Postby auctioneeral » Sat Feb 14, 2015 8:27 am

I would pull carbs. off. And bench test. Place carb rack on work bench, Run a fuel line from carb inlet to about 4-6 feet above rack and let fuel run in to carbs. That way you can see where fuel is leaking at.

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Re: Fuel leak from plenum (#3 Carb?)

Postby RBGERSON » Sun Feb 15, 2015 7:57 am

Like this with caps off so you can see into the throat of the carbs..level the carbs on the bench, small level across the plenum..wedge under the intakes to get it level. My tube not as high as it should be to get 2-3 lb.s pressure but it works for me.

Also putting some paper in the plenum helps to Id the leak source. If it's in there.
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HAD LOTS OF GOLDWING 75-83
NOW INTO 1500'S..RIDING A 1998 SE

FAIR WINDS,
RB

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echinus1988
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Re: Fuel leak from plenum (#3 Carb?)

Postby echinus1988 » Mon Feb 16, 2015 6:21 pm

I have my work cut out for me but it keeps geetting compleated in that the fuel leak has stopped AGAIN! It seems to come and go on its own.

I had it out the other day to take it to my son's so he could help me look it over. By the time I got home, it was stopped again. I left the bike idling in the garage for close to 5 minutes and not a drop of gas. I have more to do and the bench test is high on my list if I see it start leaking again. Not sure if the bench test will help at this time but I see the set up and it's pretty simple.

Thank you again to everyone. I will let you know if I get this figured out. But then, I plan on getting my 1982 Aspencade up and running which means this will go to my son! He might get the fun and thrill of searching this leak down!

Steve

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Re: Fuel leak from plenum (#3 Carb?)

Postby WingAdmin » Tue Feb 17, 2015 11:26 am

Is it possible that the leak occurs only when it is cold?

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echinus1988
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Re: Fuel leak from plenum (#3 Carb?)

Postby echinus1988 » Sun Feb 22, 2015 1:46 pm

Leak only occurring when it's cold?

I don't recall any leaks during the summer so that is a possibility. One of the seals shrunk? The crossover tubes from carb to carb did not get new seals since the rebuild did not have them (a problem corrected on the Aspencade!) but I don't see how that would affect the gas flowing into the plenum. Am I missing something?

It does appear to stop after the engine is warmed up. I haven't watched close enough to see if that is always the case but I believe it is. I started it yesterday and it immediately started leaking again. I didn't keep it running to see if it stops when it warms up. One more thing to check.

With the snow, I'm sidelined for a while. Time to work on the Aspencade again. Cleaning out the gas tank next so I can get the reserve working again. At least it runs with no gas leaks, just don't have the last one gallon of gas available yet. Next new tires and I'm ready to go on our 2600 mile trip this spring!

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Re: Fuel leak from plenum (#3 Carb?)

Postby Mindslyder » Thu Mar 26, 2015 7:12 pm

So my father (echinus) has finally pulled the carbs to replace the plenum gasket, which is where we feel the leek is coming from, and has decided to replace the o-rings on the gas feed tubes inbetween the carbs while he has them off. (he didn't replace them when he rebuilt since they weren't in the kit) Only problem, we cannot find the size for the o-rings anywere!!! He did put an o-ring in but it ended up shaving a little off as it went in, indicating it is to thick. but of course all we really have immidiate access to is SAE. Can anyone help us?
Thank you

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spiralout
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Re: Fuel leak from plenum (#3 Carb?)

Postby spiralout » Sat Mar 28, 2015 12:47 am

Mindslyder wrote:So my father (echinus) has finally pulled the carbs to replace the plenum gasket, which is where we feel the leek is coming from, and has decided to replace the o-rings on the gas feed tubes inbetween the carbs while he has them off. (he didn't replace them when he rebuilt since they weren't in the kit) Only problem, we cannot find the size for the o-rings anywere!!! He did put an o-ring in but it ended up shaving a little off as it went in, indicating it is to thick. but of course all we really have immidiate access to is SAE. Can anyone help us?
Thank you

The o-rings for the larger pipes are 5.8 x 2.0 mm and the smaller pipes o-rings are 2.8 x 1.3 mm

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Re: Fuel leak from plenum (#3 Carb?)

Postby Overdog » Sun Mar 29, 2015 8:19 am

Get it running and watch #3 carb when you twist the grip to operate the accelerator pump. Sounds like you may have some crud blocking the accelerator pump passages. Mine lost power a few times last season, then cleared up......with the end result that the pump went bad and was squirting gas upwards from around it's shaft.

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echinus1988
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Re: Fuel leak from plenum (#3 Carb?)

Postby echinus1988 » Sun Mar 29, 2015 11:16 am

Well, I took the carbs out, replaced the seals around the gas crossover and accelerator lines. One of the gas crossover tubes had the Lucas gas treatment and dirt all around it so that was part of my problem.

I say part because I cleaned and put everything back in and crossed my fingers that I had it resolved based on where it was coming from.

I turned on the gas, pulled the choke and the bike started right up. Unfortunately so did the gas leak. I got under the carbs and looked. I shut the fuel off and of course, this stopped the leak though the bike kept running (can we say, rebuild time for the petcock?). The bike ran but no gas leaked during that time. I opened up the fuel and was right there on the right side of the bike to see where it came first.

The leak started from the carb where it meets the plenum. Strange thing is that the gas didn't go into the plenum like it did before. So part of the problem has been resolved but the leak remains.

My son suggested blowing air through the gas line into the carbs so I disconnected at the pump and blew air into the carb. Only used about 2-5 pounds of pressure to make sure that it didn't blow anything out. Results were I could here air blowing into the plenum, gas was blown into the plenum near carb three. Now does this tell me anything? Not sure yet, but I am hoping someone here has more experience and can tell me. The more I think of it, the more I think it doesn't. Even that low of pressure is probably enough to move the float needle jet and let air into the bowl blowing gas.

What I am trying to figure out is, am I on a wild goose chase? The gas is coming from somewhere. The other three carbs do not appear to have any gas around them, the gas appears to be dripping from the connection between carb #3 and the plenum, it also drips from the tube crossover under the plenum but that is a low spot, I don't see any gas spraying from the bowls.

Is there an overflow that might indicate a stuck float valve? What am I missing? I have not set up the fuel feed to bench check it due to limited funds but I guess I might need to do that.

Before I pull it again, any suggestions would be appreciated. Thank you all for your help.

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Re: Fuel leak from plenum (#3 Carb?)

Postby auctioneeral » Sun Mar 29, 2015 1:09 pm

check this site for carb break down.
http://randakks.com/collections/honda-g ... master-kit

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Overdog
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Re: Fuel leak from plenum (#3 Carb?)

Postby Overdog » Sun Mar 29, 2015 2:32 pm

With my accel. pump issue the gas wasn't spraying from the bowl....it sprayed upward around the shaft, then dripped down from the area you say your leak seems to be coming from. It wouldn't leak unless the grip was twisted, operating the pump.

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Overdog
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Re: Fuel leak from plenum (#3 Carb?)

Postby Overdog » Sun Mar 29, 2015 3:03 pm

If you've got the carb rack off you can just use a long piece of fuel line to connect the rack to the petcock with the rack sitting on an upside-down 5 gal bucket or something else of the proper height.

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Re: Fuel leak from plenum (#3 Carb?)

Postby littlebeaver » Sun Mar 29, 2015 3:19 pm

+++ 1 on the Bench tests..

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echinus1988
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Re: Fuel leak from plenum (#3 Carb?)

Postby echinus1988 » Sun Apr 05, 2015 12:48 pm

As usual, I look for the difficult issues when it's really simple.

The seals between the plenum and the carbs had gotten old and brittle. I got the set from Randaaks and installed them.

I put the carbs and plenum back together, reinstalled and then started it. It ran great!

Now I'll readjust idle jets, sync the carbs and then be ready to ride.

Almost actually, While I had it apart, I am replacing the thermostat, putting in my new timing belts. Getting it ready. Then do the same for the 1982 Aspencade.

I had a problem with a clogged fuel line in the aspencade, used an old choke cable, attached it to a drill, sprayed WD-40 into it, ran the cable and cleared the line. I now have my reserve again!

Thank you for all your help!
Steve




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