Help......float Bowl Leaks

[GS750GUY]

Dear GS family, GS750Guy here again.
I recently rebuilt the carbs on my 78 GS750EC and very carefully removed and meticulously cleaned the gasket surfaces for the float bowls. I bought new gakets and to the advice of many and the manual I used nothing but the gasket to seal the bowls. Welllllllll guess what. After returning from my first ride last fall I noticed gasoline sitting in low spots on top of the crank case. With further investigation I noticed drips of fuel hanging from the bottoms of the bowls. My initial thought was that it was the tubes connecting each carb but further inspection showed they were all dry as a bone and the only wet fuel I found was from the top edge of the bowl where it fastened to the carb body on down.
I'm tired of fighting gaskets and bowl leaks. Is there any liquid gasket sealer that I can use sparingly in conjunction with the gaskets that will seal the &*%^%$$##@#$% bowls and still be fuel resistant and not find its way into the fuel system???
I appreciate all your wisdom on the matter.
GS750Guy

 

[Nessism]

You are on the wrong track regarding the source of your leaks, float bowl gaskets are to go on dry - you will NOT have a gasket leak this way unless the gasket surface is gouged out. Sounds like you have a leaking float needle or fuel T fitting. Check things more carefully and even consider checking the carbs while they are on the work bench - fashion a fuel feed source of some sort and watch like a hawk. Dollars to donuts the float bowl gaskets are fine.

 

[Greg O.]

I have not had a bowl gasket leak. Maybe one was installed improperly? Is any gas running out the overflow tubes?

Greg O

 

[oldschoolorange]

If you used new gaskets and installed them properly check your float heights
. Try not to use silicone on your float bowls as carb passages and silicone do not mix well. If you ever need something like that Detroit Diesel has a product called gasket eliminator ( I think permatex makes it ) I have used it adn had no problems as it only cures in the absence of air

 

[bwringer]

It ain't your float bowl gaskets.

Gas is overflowing or leaking from elsewhere. The most common cause is a worn-out petcock combined with mung holding the float valve needles open.

For the love of all that's good and holy, PLEASE don't put any goop on your float bowl gaskets. Foreign substances do NOT belong anywhere NEAR your carbs.

Even the nastiest, grungiest, torn, flattened, 25 year old float bowl gasket will easily form an adequate seal.

Again, the problem is NOT your float bowl gaskets. Find the real source of the leak.

 

[GS750GUY]

Thanks guys!
I checked the float level, checked the "T's", and I am not getting any fuel through the overflow tubes.
I only see evedince of wet fuel from the gasket on down to the bottom of the bowl. There are no signs above the gasket. When I shine a bright light at the edge of the bowl I can see the exposed edge of the gasket. On three of the bowls I can see wet gasket material through the small space betweent the edge of the bowl and the bowl body and no signs of fuel higher than the level of the bowl gasket.
It could be I may have nicked the small raised metal ridge that surrounds the gasket surface when I was cleaning off the old gasket material. It probably would not take much of a nick in the metal surface to create a leak.
The leaks are not horribly bad just enough to cause an ocassional drip. But any leak is too much. Do you suppose in time when the gasket seats well that the leak would stop?
In the event I have created the leak by nicking metal it would seem my only alternative would be to use some kind of sealant. Surely I would think there must be some GS'rs out there that have found a successful method of sealing the kind of leak where the surface has been compromised.

GS750GUY

 

[jadesystem]

You probably will need to remove the carbs and rebuild them again.
Inspect the body for hairline cracks, bowl gaskets, o-rings, needle
valves and seal it tight with the recommended torque. Adjust the
float so that gas is cut off completely at float level at the inlet
needle valve(s). I use a 10mm hose hooked-up to the carb inlet
nipple. I blow air into it, and then I move the floats up and down
to see if it cuts off. If it is not level, I bend the tang so that it is
correct.

As the carbs are off the bike, I'll even use water to test the floats
in the carbs once they are rebuilt, then blow out the water residue
with compressed air, wipe it clean, or chase it out with gas. Not a
big deal using water as some might be alarmed of this. It is only
going through the needle valves and onto the bowls, and not being
sucked and drawn-in by vacuum. I don't recommend using water in
place of gas in the tank for T/S purposes, as it will start to rust immediately. But the carbs is OK. The carb body is somehow
impervious to rust.

One time, I used water in the tank to troubleshoot my GS1150
gas tank float level circuit. I don't like working around gas as it has
high vapor pressure seeking an ignition source...and especially when
gas is $4/gal. I'd rather be safe than dead !! Rust started to form even
though the water was chased out with gas. I'll probaly use a rust
inhibitor to mix with the water the next time I work on this gas tank
float sensor issue.

Good luck to you :-D




Make sure each carb bowl drain plug is tight with a new 0-ring or
washer gasket. Don't use a sealer, as new bowl gaskets should
seal well and be sufficient enough.

 

[jadesystem]

Any gas leak, either a small drip to a siv, is no good and is outright dangerous. Could cause a fire and there goes your machine. And at
$4/gal, you want to conserve every drop.

\\/

 

[Nessism]

As silly as this sounds, did you tighten up the floatbowl screws fully? Hate to admit this but on my 550E the screws were loose which caused a leak from the floatbowl. Snug the screws down pretty firmly - you need some gasket compression.

 

[Steve]

The only time you will see leaks from the overflow tubes is if the floats are stuck open and the leaks at the bowl gasket are slow enough to let the fuel level climb.

Because your overflow tubes seem to be dry, it is possible that the float level is seriously off, or one of them is stuck. When things are all set properly, the fuel level is below the bowl gasket about 5 mm, so the only time the gasket might get wet is when accellerating or decellerating hard enough to slosh the fuel around in the bowls.

.

 

[t3rmin]

I always wet my bowl gaskets with WD-40 before installing. I feel like that makes 'em a bit more malleable. I've never had a leak from the float gaskets, but I have had a darn annoying leak from the between-tubes.

It's very frustrating when that happens after taking years off your life with the struggle to re-seat the carbs in the airbox boots...

 

[hampshirehog]

You can get decent petrol resistant gasket sealer - blue stuff I've got in the garage is fine but I can't remember what it's called. However, the name is irrelevant here as you can't use sealant on your float bowls. The reason: if you have a look at the gap between the side of the bowls and the floats you'll see that it's next to nothing - even some aftermarket gaskets need trimming to fit. If you put sealant in there thick enough to cover, the chances are that you would squeeze some sideways and interfere with the free movement of the float.

 

[jadesystem]

The carb bowl gaskets were not meant to have sealent whatsoever.
The gasket is sufficient enough to provide a good seal if all 4 screws
are tightened in-place and both the mating surfaces are clean and flat.

The spongy characteristics of the gasket will absorb a tight seal
shielding the outside elements.

:-D

 

[SqDancerLynn1]

My question is DID you use OEM gaskets ? some of the Ebay gaskets are thinner than stock, could cause problem ???

 

[Zooks]

As silly as this sounds, did you tighten up the floatbowl screws fully? Hate to admit this but on my 550E the screws were loose which caused a leak from the floatbowl. Snug the screws down pretty firmly - you need some gasket compression.

This was my first thought. Get your screwdriver out and (carefully) apply a little extra pressure to the screws. If you have 'nicked' the surface of either the bowl or the carb body the gasket should be more than enough to make up for it. The gasket is, after all, there to make up the difference between the two surfaces.

I agree with the majority here that sealants near the carbs is a bad idea.

 

[GS750GUY]

My question is DID you use OEM gaskets ? some of the Ebay gaskets are thinner than stock, could cause problem ???

You know....that's a thought! I got the gaskets from one of the bike parts houses.....not from Ebay. But they seem awful thin. Hardly thicker than a piece of craft paper And they seem harder and more brittle. Could be this is the problem.
However, I talked to a guy this week that has many years of bike experience and has rebuilt many sets of carbs over the years. He said once in a while he would get one of those carb bowls that had such messed up contact surfaces no gasket would keep it from leaking. He said if you use Permatex Ultra Rubber Gasket Sealant and Dressing (which is fuel resistant and non-hardening) and use it on the very outside edge of the gasket and use it VERY VERY SPARINGLY...he said it stops any problem leaky surfaces and used sparingly at the very outside edges will not squeeze out and interfere with float function or cause fuel problems.
I think I will seek out thicker gaskets and use the above only as a last resort. Problem is you don't know what you are going to get until after you have gotten and paid for them.
GS750GUY

 

[GS750GUY]

I always wet my bowl gaskets with WD-40 before installing. I feel like that makes 'em a bit more malleable. I've never had a leak from the float gaskets, but I have had a darn annoying leak from the between-tubes.

It's very frustrating when that happens after taking years off your life with the struggle to re-seat the carbs in the airbox boots...

Your WD-40 suggestion is a good one and reminded me that someone else suggested sparingly coat the gasket surface with a heavy non-fiberous autmotive wheel bearing grease. The theory is the heavy thick grease compressed between the imperfect contact surfaces would make it very difficult for fuel to get through.
GS750GUY

 

[Nessism]

You seem dead set on putting some sort of monkey snot on the gaskets for some reason. Floatbowl gaskets are designed to be installed DRY. Period. They will not leak unless the screws are loose. Mikuni has built millons of carbs...all with dry floatbowl gaskets. Follow their lead. They are the experts.

 

[GS750GUY]

You seem dead set on putting some sort of monkey snot on the gaskets for some reason. Floatbowl gaskets are designed to be installed DRY. Period. They will not leak unless the screws are loose. Mikuni has built millons of carbs...all with dry floatbowl gaskets. Follow their lead. They are the experts.

Thanks Nessism. I will get a new set of OEM gaskets, try them dry and see what happens.
Thanks for your wisdom!
GS750GUY

 

[jadesystem]

I love the Permatex red gasket sealer. Excellent product and very cheap
at $5 per tube. Not recommended for sealing a gasket for your carbs.
Anything it not your carbs !!

As Nessism sez, don't use it !! On a valve cover gasket, it works beautifully. Easy to remove too like peeling an orange. A lot of
uses which is high temp, and impervious to gas and oil. This I
recommend to bring along on any road trip.

:-D\\/