Fuel Tank Leak Mystery -- help needed

[thunderbolt]

I have a fuel leak and cannot work out where it is coming from. Need your help and advice if you have any experience with these fuel tanks leaking and what the remedy is.

The other night I went into my workshop (shed) and saw a petrol stain on the Rh side frame rail directly under the tank. I felt up under that bside of the tank and was able to wipe reddish residue away.

So I removed the tank ('03 model) expecting to see a leak around where the hoses fitted onto the underside of the tank or around the fuel sender unit. But nothing as seen below. These pics show areas where there is definitely no leakage present.







The following pics show the area where there is fuel residue where the tanks mounts at the rear to the frame.









There is more residue on this area on the LH side under the bar. Not so much on the actual tank as seen below.





If anyone has had a fuel leak from their tank their experience in where this leak may be coming from would be helpful. I am thinking it is coming maybe from under the welds of the rear tank mounting points at the rear of the tank.

Do these late model tanks have any common areas where they are prone to leak?

Any help from those more experienced in this stuff than me will be most appreciated.

I need a solution to the problem as well as pinpointing where the leak is coming from.

Thanks for any and all help offered.

[Wicky]

Do normally have the tank overflow drain hose fitted?

If you fill the tank up while it's off the bike with some kitch roll underneath then that should give an indication of where its leaking. (put some spare 10mm ID fuel hose on the spigot and clamp it shut).

Check condition (esp for splits) in the exiting fuel line hose - and that it was secured with a clip or clamp.

[bsabloke]

I have used petropatch, on cars & bikes over ther years. Always works & never a problem.
Small bottle of nail varnish type stuff, in a bottle with a brush in the lid. & a piece of cloth patch.
Clean area, cut patch, paint layer of liquid, apply patch, paint another layer of liquid on top.
I have used just liquid when not practical to use cloth patch.
Once used on bottom of leaking car tank on top of the petrol dripping out & it worked.
A good short term solution

[Varastorm]

I had a friend who bought a Gsxr 1000 k2 that had been stored in a conservatory Best place to store a fuel tank if you want it to rust internally.

Over a period of months we tried all sorts to cure the leaking teabag tank, total waste of time.

Don't try & weld it as you'll get an orange wheel chair sticker for life.



Save yourself a lot of time heart break & get rid & get a second hand one from eBay

If you can't find one in your colour get a tankbag cover to hide the wrong colour tank till you find a tank that'll do you, then flog them both

[darkember]

Best way to find it would be to use a compressor and soapy spray.

[sirch345]

It looks more oily than petrol to me, are you definitely sure it's a petrol leak

Chris.

[thunderbolt]

I had a friend who bought a Gsxr 1000 k2 that had been stored in a conservatory Best place to store a fuel tank if you want it to rust internally.

Over a period of months we tried all sorts to cure the leaking teabag tank, total waste of time.

Don't try & weld it as you'll get an orange wheel chair sticker for life.



Save yourself a lot of time heart break & get rid & get a second hand one from eBay

If you can't find one in your colour get a tankbag cover to hide the wrong colour tank till you find a tank that'll do you, then flog them both

Thanks Varastorm, good suggestion but do you realise how rare these 19l. tanks are? Like hens teeth. I will keep a lookout though.

[macdee]

had a problem like this with a mates bike
wash and clean the area with soap and warm water then dry
get the tank up on something that you can sit back with a beer a watch where its coming from
the problem we had was that the leak was about an inch way from where the fuel appeered ,its was creeping under the paint
the air compresser is good but sometimes hard to set up if you dont have the gear

in the first two pics theirs is a little bit of weld missing where the bracket is welded to the tank ,looks a good place to start

[darkember]

It does look like it was faulty from new.

[thunderbolt]

the air compressor is good but sometimes hard to set up if you don't have the gear

in the first two pics theirs is a little bit of weld missing where the bracket is welded to the tank ,looks a good place to start

Yes this area at the rear of the tank is the area I suspected as well.

I sprayed the area around the broken welds with soapy water and directed compressed air into the petrol outlet opening on the bottom of the tank and covered the small breather pipe with my finger (couldn't find a cap small enough to fit over it's opening). I did not need to block off the drain pipe on the bottom as the other end of it is above where the tank fuel cap seals so is not pressurised when air is put into the tank. The result was that there were no soap bubbles obvious when the tank was pressurized.

Interestingly though when I pressurized the tank through the fuel outlet and had not covered the vent pipe in the tank, fuel came spurting out the vent pipe a couple of feet into the air. I guess the vent pipe end inside the tank was sitting in the small amount of fuel left in the tank and it was blown up through the vent pipe. The tank was upside down when I did this test. Hence my putting my finger over the vent tube when doing the secondary test after nearly getting a gob full of petrol in the primary test. When I did this test there were no bubbles evident as I spayed soapy water around the suspect area.

A warning for anyone doing these types of tests. Careful not to get a faceful of petrol - wear protective eye wear.

My plan this afternoon is to do the same test again. Cover in soapy solution and use compressed air to pressurize tank again (low pressure) to check for leaks. Then I will plug the tubes at the bottom of the tank and 1/2 fill the tank with fuel and check for physical leaks with kitchen towel underneath to make a leak more obvious. If I cannot find any which I suspect I won't going be my previous test then I will have to look elsewhere for the leak.

[thunderbolt]

It does look like it was faulty from new.

I think the fact that there are gaps in the welds is not an issue. I think the welds on the tank base are to hold the mounting bracket in place and do not have anything to do with sealing the tank - unless one of the welds gets too much penetration and goes all the way through. Not likely with MR HONDA in 2003 me thinks.

Thanks for the contribution though.

[thunderbolt]

To recall this thread after a bit of a lapse.

After having had a look at the photos again I am thinking maybe the leak is from the fuel tap (or whatever it is called) in front of the area moistened by the petrol residue.

It looks like the petrol could be weeping from the diaphragm joint of the fuel tap (??) and blowing back on to the plate which the tank mounts to and causing the stain.

See pics below and opinions valued:








If this is where the leak is from, Are these items (fuel tap) obtainable? Can a kit be purchased to repair the fuel tap?

Thanks for opinions offered.