Leaking Gas Out of Airbox overnight

johnjones750csr wrote: ok, I think we are talking about a different tube here. The overflow on my carbs (the second T fitting) is not hooked up to anything. The fuel is not coming out of there. the fuel is draining out of the bottom of the airbox and the only thing that is hooked to the air box is the airflow tubes that hook to the carbs. There is no overflow running into my airbox and the fuel is not coming out of there. there is nothing wrong with the float bowl at all. the tube that is cracked is the little tiny brass one that slides into the float bowl when you put it on.

Perhaps an enrichener pick-up tube, which being cracked won't cause gasoline into the airbox.

Where only the airbox hoses are connected between the airbox and the carbs, and gasoline is flowing "backward" through the airhoses (or one of the air hoses), it's likely gasoline that's risen up into the carb bore due to leaking float valves or other issue, together with an improperly functioning petcock that's failing to disallow fuel flow when it's supposed to.

Would examine and sniff-test the crankcase oil to determine whether the oil has been contaminated with gasoline.

Good Fortune!

Replace the float needles and seats. I had the same problem on my 1984 ZN1100 and some new float needles and seats cleared up the problem. Just fixing your overflow isn't likely to fix the problem. It is only going to make sure that the overflow is routed somewhere other than your airbox. The key is to stop the overflow.

(sorry, my post somehow double-posted, so I deleted this one)

I'm suspecting your petcock.

How could your airbox end up with gas in it?

Only one way: the carbs are filling up with gas to the point where the gas flows from the carb to the airbox.


Now, if the petcock was not flowing gas -- that could not possibly happen.

There's simply no way for your airbox to have all that gas *unless* it came from the petcock.

And the thing is, if you have a vacuum-activated petcock -- which I think you do on that model -- there should NOT be *any* gas at all coming out of that tank.

EASY WAY TO CHECK.

1) unplug all the hoses that are attached to your fuel petcock -- there is probably one rubber hose that connects to the back of the petcock, and a larger rubber hose that connects onto the side of the petcock. The larger rubber hose is the gas line; the hose that connects to the back is a vacuum line that connects to one of the carbs and when the motor turns over, the suction from the engine pulls open a rubber diaphragm inside the petcock to let fuel flow.
If you have a vacuum-operated petcock, there won't be an "Off" setting, only 'On' and 'Res' and 'Pri' (prime).

2) if you don't have a vacuum operated petcock, you instead should have an 'Off' setting, and it should have been set to 'Off' every night after you're done riding -- perhaps that was the trouble? If so you're done.

3) put a largish rag right underneath the petcock -- to catch gas. Don't remove the tank here, we want to reproduce the symptoms exactly -- leave the tank on the bike.


4) Next day, wake up -- if the rag is soaking with gas, which I suspect it will (unless you have a normal petcock and you failed to set it to 'Off' at the end of the day) that shows your petcock is still leaking.

How could this happen, a leaking petcock, after a rebuild? Heck I've done it myself, I usually put something back together backward, like the black rubber circular piece that goes right behind the lever.

There's no way your carb could spill all that gas into the airbox unless it's being filled with gas coming from the petcock.

I would turn the petcock to the off position asap.

you probably have a carb with a needle thats sticking open and allowing gas to pour out of the seat all night. Make sure you check your oil to see if its contaminated with gasoline. It can get in through the PCV breather that links to the airbox (if your motor is like the one in my 81' KZ1000LTD) or an intake valve could've been open when the motor was shut off last time and gas can pour into the cylinder and past the rings, into the crank case. Check and make sure its not the petcock on the gas tank. I'd give it a chance and maybe try to rebuild it if it does leak. If you suspect a carb has a sticking float valve (needle and seat) give the carbs a good thump with a rubber mallet. I used to do this everytime i came home from a ride before i finally made my own gas tank valve.

Someone else mentioned to check the crankcase to be sure you don't have gas in the oil. VERY bad to start the bike in that condition. First check the level of the oil to see if it is higher than it should be and then take some oil out through the filler hole and give it a good smell test. If you even think gas got in there drain it and change the oil and filter.

I had the same problem when I got mine, I put the vacuum hoses on the bottom of the carbs in the bottom of the airbox and went riding. I had no problems until I got home and gas was all over the porch. they are vents for the floatbowls and setting the vacuum hoses inside the airbox, if that is what you did will suck the fuel and sink the floats with the vacuum in the airbox.

ok, the petcock is still leaking, even after I rebuilt it. I put everything back together the same way I took it apart. Does someone have an assembly diagram for the petcock just so I can double check that I got everything right?

ok, so I dissassembled my petcock and discovered that the reason why it would not stop the fuel from flowing is becasue it was clogged with rust everywhere. So now I'm having two issues with my tank. The previous owner coated it because it's rusty, and apparently they didn't do it right and it's peeling off inside the tank and I can't reach it to peel it out. And now since the coating is now coming off, the rust is settling at the bottom of the tank right in my petcock. Thank god I put a fuel filter on it recently or else I'd have a real mess.

How does one de-rust a tank without using a coating? is there some product out there that will get rid of the rust?

thanks

JohnJones750csr

it is pretty simple, is it a vacuum petcock?

johnjones750csr wrote: ok, so I dissassembled my petcock and discovered that the reason why it would not stop the fuel from flowing is becasue it was clogged with rust everywhere. So now I'm having two issues with my tank. The previous owner coated it because it's rusty, and apparently they didn't do it right and it's peeling off inside the tank and I can't reach it to peel it out. And now since the coating is now coming off, the rust is settling at the bottom of the tank right in my petcock. Thank god I put a fuel filter on it recently or else I'd have a real mess.

How does one de-rust a tank without using a coating? is there some product out there that will get rid of the rust?

thanks

JohnJones750csr

I use a product (not a sealer product) called "Klean Strip Phosphoric Prep and Etch"
This product contains Phosphoric Acid -- this type of acid eliminates the rust. Phosphoric Acid is also, I believe, part of the 'tank sealer' products you can buy. Put some in the rusty tank (remove any fuel sensor and petcock first -- I tape off the holes using Gorilla Tape, man that Gorilla Tape will survive a nuclear attack) then slosh it around and flush it out with water, then fog it with WD40 or if you plan on putting the tank in service right away, put a small amount of gasoline right after you flush it with water. Slosh the gas around to make sure the entire innards are wet with gas then open the cap and drain the gas and let it air dry. Should be ready to go after that.


Here's what it looks like:



And if you've never seen it, this tape is very useful for sealing off the holes in the bottom of the gas tank after you remove the petcock etc. to clean the tank.



I have tried lots of different types of tapes -- and only this Gorilla tape, when applied to cover the petcock hole (clean well around the hole though, clean it well).

This Gorilla tape has held up for me after partially filling the gas tanks I clean for the following liquids:

1) lacquer thinner (to remove old gas remnants from the tank)

2) gasoline

3) phosphoric etch liquid


I've cleaned many a tank -- the Gorilla tape holds to cover the holes left by the removed petcock, fuel level thingie, etc. Every other type of tape I've had dissolves the tape or glue.

So for a few bucks you can buy Phosphoric etch and gorilla tape and BAM tank is back in service.

Always use an inline fuel filter though.+