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Discussion Starter #1
Hey guys...
Driving me crazy - - - I have replaced every seal and every hose in the tank. the bike is still leaking fuel.

Starting to think it is the tank itself. This bike sat for many years full of fuel before I owned it.
Bad gas caused me to replace every thing inside the tank when first purchased. I was great for a few years - then the fuel leak.

MV Miami has replaced everything again.. all the seals the hoses the pump the sensor - - no luck.

Has there been a problem with F4 tanks failing? I look inside and can see seam sealer - is that a possibility?
I do not use ethanol fuel anymore - but running it was the norm for many years.

Will MV reseal my tank if I send it to them? seems to be leaking down faster now then before.
Thanks,
Jeff
 

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Check the Maintenance and Tech tip section mate, lot's of threads on this topic.
Do you realy feel MV should take responsibility for a tank that maybe more than 13-14 years old ?
FWIW - No the F4 steel tanks are not prone to leaking through the body - surely you can see what it looks like inside - or find where the fuel leaks from ?

Or just buy another one, heaps on the market.
 

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Hey guys...
Driving me crazy - - - I have replaced every seal and every hose in the tank. the bike is still leaking fuel.

Starting to think it is the tank itself.
Jeff

Jeff, where is the evidence of tank leakage? i.e. where do you see fuel?
 

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Discussion Starter #4
Do you realy feel MV should take responsibility for a tank that maybe more than 13-14 years old ?
absolutely not - - I am willing to pay- just thought the original manufacturer might do that work, if it is a known problem.

It is dripping down to the bottom of the fairing then on to the floor can't tell from where yet- - gonna remove the body work tonight and try and pressurize the tank.

The 2 specialists went through everything :frown2:
 

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Do not pressurize the tank!!!!!

That tank will deform with very little pressure.

Gravity is your friend.

Fill the tank, open the lid, use a flashlight (for God's Sake no flame!), and look for the source. If it is from the fuel pump plate, the drips will show up on the lower left corner of the tank.
 

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Discussion Starter #6
Do not pressurize the tank!!!!!

That tank will deform with very little pressure.

Gravity is your friend.

Fill the tank, open the lid, use a flashlight (for God's Sake no flame!), and look for the source. If it is from the fuel pump plate, the drips will show up on the lower left corner of the tank.
OK - thank you.
 

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Hahaha - "No Flame" so funny but so possible, I've seen a woman do that, she so "lucky" that her husband back-handed her before she got the lighter close enough to the tank.
 

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I had a strange leak once, so on the off chance it's the same....
It was the o-ring on the connector that goes into the tank, not the one that was on the connector but the bit of old o-ring that was stuck inside the fitting in the tank.
Didn't leak until the fuel pump pressurised.
 

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#1 Distinct possibility it is emerging from the overflow hose .

Possibly not connected correctly inside the tank..Possibly split. Possibly the tank is over full and it is just doing it's job !

Have a look at the end of the overflow hose and see if it is wet with petrol.

#2 Possibly a male fuel connector O ring was damaged on assembly. It is very easy to do this.

#4 Possibly the fuel pump flange O ring has been damaged on assembly.

But I reckon it is the overflow hose as surely a minor fuel leak from higher up would have evaporated before it gets down to the ground...Possibly !

Joe
 

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I have an idea might be a long shot. On the market you can get UV dye for oil leak checking also freon for AC systems. Anyone think it can be added to the fuel?? All you need then is a inexpensive UV light to look for the blue stain.

Also recently used a Ridgid bore scope which might be safe to use to inspect the inside. You'll have to do more checking first it does have a light on the end. It was very affordable well built for like $150. It was designed for plumbing I think. Or you could just drain the fuel first.
 

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@pacecarjeff: Some questions.

1. Is the fuel dripping out of the overflow hose?
2. Is the fuel running down the outside of the tank bottom from the fuel pump plate, then finding the low point?
3. How full is your fuel tank?
4. Does the fuel leak appear when the fuel pump is off?
5. Does the fuel leak get worse when the fuel pump primes?
6. Removing the tank is a simple affair, do you feel confident doing that?

There are only certain pathways for fuel to get from inside to outside of your tank. There are internal lines from your fuel cap to the drain line that can split or weep or simply have deteriorated to the point of failure. THere are seal o-rings from the pump plate to the tank that can fail in a multitude of ways. And there are o-rings in the fuel line connections that can fail in varying ways.

Knowing the answers to the above questions, in simple terms, can help us help you.

In rare cases, the fuel tank can, and has, developed a leak at the lower rear corner due to rubbing.
 

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Chuck, I'm on board with your thinking about not using pressure to check the tank since the scary thought of someone putting access amount of air from a shop compressor is most likely going to cause instant damage.

However a few years back I had to have a aluminum fuel tank replaced in a boat. I remember a conversation with the tank builder and he said it had to pass a 5psi test for certification. I confirmed with a friend recently retired form Viking Yachts that they do a 3 to 4 psi test. I think this is over 24 hr period.

If you could adapt a radiator pressure tester to the tank you'd have very good control of the desired pressure you want to use. Then a soap solution or leak test fluid on the suspected area's to see what bubbles.


any thoughts?
 

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Most people have a hard enough time actually discerning where a static leak originates let alone removing a tank, prepping it for pressure, and then pressurizing the tank for a leak check. A mistake in that process costs the performer one tank.

It's a static leak that flows fuel at static pressure. It should be easy enough to find without special tools or techniques if you are methodical.
 

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Most people have a hard enough time actually discerning where a static leak originates let alone removing a tank, prepping it for pressure, and then pressurizing the tank for a leak check. A mistake in that process costs the performer one tank.

It's a static leak that flows fuel at static pressure. It should be easy enough to find without special tools or techniques if you are methodical.
yes but what I was suggesting was a fixed safe pressure to test & a tool to use that wouldn't cause any damage. #3 post just with safe guidance :wink2:
 

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wtf????

1st there is no overflow hose.....
there is a water drain hose and a vent hose
they are wyed together under the fuel pump plate, they dump by the side stand

this failure was sudden.....
either of the hoses failed inside the tank or their connections did, they are to be replaced every 3 years

bet they weren't

remove the tank, remove the fuel pump plate and tell us what you find

:wink2:
 

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1st there is no overflow hose.....
there is a water drain hose and a vent hose
they are wyed together under the fuel pump plate, they dump by the side stand

this failure was sudden.....
either of the hoses failed inside the tank or their connections did, they are to be replaced every 3 years

bet they weren't

remove the tank, remove the fuel pump plate and tell us what you find

:wink2:
Youre right Noel..The hose does divert water from the cap well to the outside..But But But If you do overfill your tank and or expansion takes place surely the petrol will flow out via the same drain... Same diff anyway as if there is a split or lose joint in the water drain hose or vent hose you lose your fuel load...Always struck me as bit of a weak point !

Joe
 

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@gotojoe: Yes and that has happened to me! I had replaced the internal lines that run from cap to plate and one popped off on my way to a dyno run. It got exciting for a bit as the rear got very greasy as the fuel emptied directly in front of the rear tire!

I pulled up to a convenient stop, got off the bike and folded the drain line over to stop the leak. Now I was stuck standing there. An old codger came out of the gas station store and I asked if he happened to have a zip tie. He did. I fastened the zip tie around my folded drain line and went on to the Dyno Run.

I also think the drain lines are a strong possibility.
 

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@gotojoe: Yes and that has happened to me! I had replaced the internal lines that run from cap to plate and one popped off on my way to a dyno run. It got exciting for a bit as the rear got very greasy as the fuel emptied directly in front of the rear tire!

I pulled up to a convenient stop, got off the bike and folded the drain line over to stop the leak. Now I was stuck standing there. An old codger came out of the gas station store and I asked if he happened to have a zip tie. He did. I fastened the zip tie around my folded drain line and went on to the Dyno Run.

I also think the drain lines are a strong possibility.
The waste too !

One could wonder if it would be better to seal the fecking things off and just clean the tank out once a season ? >:)
 
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