fuel leak

MIKE DAVIS
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fuel leak

Post by MIKE DAVIS »

I have a fuel leak from the overflow tube on my '79. The floats are all at 15.5mm and nothing leaks until the bike gets hot, I park it, turn the pingel petcock off and within a few minutes the gas is dripping from the overflow tube. I've checked that the fuel shut off works. It leaks for a few minutes and then stops. If I turn the petcock on when the engine is cold there is no leak?

steve murdoch icoa #5322
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Re: fuel leak

Post by steve murdoch icoa #5322 »

While the floats could be set at the right height it might be a sticking float needle.
A light rap on the fuel bowl with a wood dowel or handle can jog it enough to un-stick it.

MIKE DAVIS
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Re: fuel leak

Post by MIKE DAVIS »

i've got new float needles coming from Louis but why would it stick consistently. I was thinking of unhooking the individual drain lines to determine which one .

Mouse
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Re: fuel leak

Post by Mouse »

Parked on the side stand?
no#1 carb overflowing due to side stand parking? :think:
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MIKE DAVIS
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Re: fuel leak

Post by MIKE DAVIS »

no, I always turn the gas off and it happens on the center stand and the side stand. It's like it's leaking out what's left in the line from the shutoff to the carbs. And only when it's hot. I pulled the individual lines and will ride it to see which one leaks when I shut it down.

MIKE DAVIS
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Re: fuel leak

Post by MIKE DAVIS »

so I hooked up some clear vinyl tubing to each overflow tube, took a ride parked it on the center stand, turned the gas off and within about 15 minutes I could see vapor building up in several of the lines. It eventually condensed and started dripping, very slowly, until the motor cooled down????

Rick Pope
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Re: fuel leak

Post by Rick Pope »

Just a wild ass guess, but I'd say the residual engine heat is boiling the fuel in the bowls.
Rick Pope
Either garage is too small or we have too many bikes. Or Momma's car needs to go outside.

letxbruce
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Re: fuel leak

Post by letxbruce »

Depending on additives and the mix of components the boiling point of gasoline can range from 100 to 400 degrees F. I've noticed the same tendency on my bike so I park it outside to cool down before moving it into the garage since I have a gas water heater and don't want to tempt faith.

Bruce

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Re: fuel leak

Post by daves79x »

Rick is correct and this is why these things are so hard to start after sitting for a few days. Bowls half-full from evaporation, then what's there goes stale very quickly. That said, you are riding in the summer in NV - you might be getting the bike very over-heated. These things will run OK in 100-degree heat if kept moving, but if you sit AT ALL in that heat in traffic, you are killing the engine. They hate that kind of treatment and internal engine components and carb rubber parts will suffer quickly. Ride in the heat if you must, but do not sit and idle in it.

Dave

Mouse
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Re: fuel leak

Post by Mouse »

Turn your petcock to off about a block from home at the end of your next ride and then see if you drip fuel.
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MIKE DAVIS
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Re: fuel leak

Post by MIKE DAVIS »

I don't have a car so I don't have the luxury of not using the bike, heat or cold. I lent my son my 4-runner 5 years ago and he bought a Ducati instead of a vehicle. I'm going to put the new needles in today, reset the floats, and see what happens. Since the needles are 14 years old and the bike sat for a long time, new needles are probably in order. Other than that, the bike runs perfectly with no flat spots or hesitation anywhere in the rpm range. It starts instantly and idles perfectly also. I will definitely start shutting the gas off early though. thanks everyone for all the help.

MIKE DAVIS
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Re: fuel leak

Post by MIKE DAVIS »

Just a thought. I've been using Royal Purple fuel system stabilizer. I wonder if it affects the boiling point. I'll drain the gas and fill with plain gas to see.

letxbruce
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Re: fuel leak

Post by letxbruce »

Adding to Dave's comment on the half empty float bowls, the most volatile components of the fuel evaporate first, and it is the volatile components that aid in cold starts. After opening the fuel valve when starting the floats refill but now the total percent of highly volatile fuel is lower. At least, thats the theory that I have come up with.

Bruce

MIKE DAVIS
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Re: fuel leak

Post by MIKE DAVIS »

This thing always starts at the touch of the starter button. I took a very short ride, maybe 2 miles and after I parked it and the engine heat got to the carbs the leak happened again. I don't know why it is getting so hot but it always runs perfectly.

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Re: fuel leak

Post by ang4march »

I have noticed the same thing with my '81. Probably no more than 1 oz. of fuel leaks out of the overflow...always just after riding 20 or more miles. If I park it in the garage, it's enough leakage to get my wife complaining about the odor, but not enough to equal the contents of even 1 float bowl. I tell my wife it is marking its territory...

The carbs were completely overhauled by Jack Wagner about 1000 miles ago so everything is new...and I ride the bike an average of about 30 miles per week, usually on weekends. There are no symptoms otherwise, the engine runs and idles perfectly. It also starts right away if it hasn't been parked longer than a week. If it sits for 2 weeks or so, it make take a half dozen tries on the starter. The longer it sits, the more cranking is necessary to start it. I wonder if this leakage is normal and I should just park it outside for an hour before moving it into the garage?

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