fuel leak from tank overflow

[ross46]

Lately ive been having a problem with a fuelleak. When the bike sits it slowly leaks petrol from the tank overflow, the little spigot on the right hand side. What can cause this or where does it join and go? Thanks

[banner001]

that spiggot is the tank breather, it goes to a hole under the inner rim of the fuel cap, its to allow for gas to expand in the tank on hot days, and to make sure that vacuums dont form as you drain fuel from there.

you shouldnt get liquid coming from there usually, is it petrol or water?

it could be slightly blocked, 2 ways of cleaning it, air or a really long pipe cleaner, pour a bit of solvent in at the top then either clean it with a long pipe cleaner, or give it a blast from an air compressor.

or if its not that it could be leaking because of corrosion in the tank, the breather pipe sits next to the tank, and if it gets blocked water can sit there and eat the steel away, this manifests itself as a constant small dripping from the tank breather - best way to test this is to fill the tank, seal as best you can the breather under the fuel cap (remove the cap) and blow up the breather pipe, if you get/hear bubbles in the fuel tank you know what the problem is...

[ross46]

Ok thanks, I'll have a look, its petrol that's leaking, so the pipe goes inside the fuel tank from the spigot to the tank breather and if its rusted through then petrol will be leaking from the tank into the pipe and drip out at the bottom? Have I got this right?

[banner001]

Ok thanks, I'll have a look, its petrol that's leaking, so the pipe goes inside the fuel tank from the spigot to the tank breather and if its rusted through then petrol will be leaking from the tank into the pipe and drip out at the bottom? Have I got this right?

correct, but it could also be a buildup of fuel vapour due to a blockage, so best bet is some long pipe cleaners to clean any blockages, then with a good deal of fuel in the tank, remove the fuel cap, block the breather hole with your finger/bit of rubber etc and blow into the breather hose - see if you get bubbles in the tank...if not, then its probably not rusted through.

[ross46]

Right, help needed now! Got some pipe cleaners, blew up the pipe that connects to the overflow and it came up to the bit under the filler cap, put my finger over it and blew, no bubbles, sucked and formed a vacuum with my mouth, no leak, cleaned out the pipe and then it suddenly started pissing out fuel, have I probably gone through the pipe? Thanks

[ross46]

Right, there is a hole, I think before when I blew through the pipe the fuel was blocking the little hole but when I cleared the blockage it may have gone through, so what are my options, new tank is obviously one option but someone please tell me there's a cheaper option! Can the pipe be removed?

[banner001]

the pipe cant be removed as its physically part of the tank.

if the fuel leak is small - only a few mls a day, i would say to just leave it.

if it is more than that, say over 100mls a day, then you can plug the tank overflow tube at the bottom, but you might find it slightly more difficult to open the fuel tank, also you are going to have to watch for water getting into the tank as you wont have a way for rainwater to drain from the rim of the tank.

if you can find the hole you could try to get a bit of JB Weld, or another marine epoxy on it?

[ross46]

It looks like the pipe is copper, might be able to solder it, will take the tank off over the weekend when ive got less petrol, thanks for the help banner

[tomrowley20287]

It looks like the pipe is copper, might be able to solder it, will take the tank off over the weekend when ive got less petrol, thanks for the help banner

Don't blow yourself up.

Heat, petrol container and fumes = kablooie

[ross46]

~12.5:1 for it to ignite, very unlikely, I worked with a gas engineer and we used to smoke when checking gas Meyers because the stochiometric mixture is very unlikely and had to be 975K to spontaneously combust, but murphys law and all that

[tomrowley20287]

It's been a long time since I trained as a welder but it was impressed upon me, don't weld oil drums unless they've got a certificate to say they're clean as you'll loose your eyebrows and possibly your torso, head and arms too when it goes pop.

[ross46]

Yeah, welders will heat up to a high enough temperature to spontaneously ignite, but its the same reasons a petrol tank won't normally explode if set on fire, it has to be extremely close to the perfect air fuel mixture, though as I said before, follow murphys law and you'll be fine, "if something can go wrong, expect it to go wrong and plan for it to go wrong" learnt that off a psychologist who works with shell on the oil platforms

[Danny23]

Guys please help just bought a nice zxr 400 1993, yesterday went to fill the tank up which was fine drove home next morning fine got to work and petrol leaking from the top of the tank so on my lunch break I unscrewed all 6 screws from the top of the tank look like its coming from a hole to the left hand side when I looked in the tank looks like a small pipe running to the bottom which I think is the "breather" / drain away for overflow so how the hell wud petrol leak from the top is it the seal around the open hole and wen I opened it it was like it was compressed with air I checked all the key hole air way and it was fine blow through it air came out lol wen I opened the tank and petrol flowing around tank lip and before you guys say it please know I didn't fill the tank up too much!!!!! please help paint work starting to bubble

[ross46]

It did that on mine when I blocked up the bottom overflow, the pipe inside had split so I had a small leak, I blocked it of with some pipe and a boot, the next day the fuel had leaked over and out the top, I just got some silicone and popped it in the hole, works for me, only problem is with rain, the water can drop in. Hope this helps, Ross