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Discussion Starter · #1 · (Edited)
Hi everyone!

I'm a new owner of a 2015 model Dragster 800. Whilst I love the bike, I have a big fuel leak issue!

I've read many posts on the forum talking about cracks in the overflow channels inside the tank. This seems plausible, however, the leak in my case only happens after coming from a ride. It can leak a few litres over a number of days which eventuallystops. But once the leak stops, I can fill the tank right up and there is no leak whatsoever until the next ride!

Additionally, I tried blowing and sucking (no puns intended) on the overflow pipe whilst blocking the small holes inside the filler flange and I can see no bubbles in the tank. When sucking, it seems to hold the vacuum for as long as I keep it. To me, this suggests there probably isn't a crack in the channels, but I may be wrong!

Wondering if there are any other pointers or things to check other than having to replace the tank at almost 2 grand!

Thank you
 

· Old Wing Nut
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Welcome to the family !! Where in the UK are you located?

Just where is the leak coming from...I mean, you can see it dripping I suppose?
The fact that it only occurs after a ride is interesting. Is the tank full or at some lower level when you park it after the ride and this happens?
A blocked vent would cause pressure inside the tank which could push fuel out...but where?
Does your bike have an evaporative emissions charcoal cannister?
 

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Ed has the path started for you. The first thing we need to know is precisely where you see fuel leaking.
Is it from the overflow tube? A fuel fitting? The pump plate flange?
 

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Discussion Starter · #5 ·
Thanks for the warm welcome esq'z me, XPARAUK and silentservice703!

I'm based in Surrey, south east of the UK. We have some good roads around here but many of them have now had ridiculous speed limits and average speed cameras :rolleyes:

Back to the leak, it is from the breather/overflow pipe: the open-ended one close to the right foot peg. My bike doesn't have the emissions cannister. Reading the forum, this seems to be specific to US models and I can't find anything resembling it where I'd expect it to be.

I've checked the inside of the tank through the filler hole using a mirror and I can see the vent hoses are the same material as the tank as I'd expected from other posts. Looking at other posts, at first I thought there must be a crack in those pipes. However, there are two counter indications as I mentioned in first post:
  1. The bike starts leaking after a ride (with a full tank just before being parked as I used to do with my other bikes, but also when I fill up leaving couple of inches space and then ride for 30-40 miles. At that point there is probably room for another 3-4 litres of fuel in the tank, so it's not overflowing). It leaks slowly for days or weeks until it stops. If at that point I fill up the tank again, even if right up to the cap, there is no longer a leak until my next ride.
  2. I checked the vents for blockage by blowing through the breather pipe (one next to foot peg) and blocking either of the two holes in the flange (one for rain, the other linked to cap for vapours). I can see air flows through both so there isn't a block. I can't push air when I block both at the same time and didn't hear or see any bubbles in the tank. I also blocked them and sucked on the breather pipe and noticed it keeps the vacuum, i.e. keeps my tongue sucked in for as long as I want - very scientific I know, but proves the point :p
So I'm at a loss and out of ideas what could be happening.
 

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Well, based on what you are describing, the only solution is a leaking overflow/drain internal molded line.
I would conduct an experiment to see if the level drains/returns to the same level each time the "overflow" occurs.
Those first gen tanks are known to fail.
 
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· Old Wing Nut
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The Evap system used to be a USA model thing...it is now a global thing. You will find it on newer models in your country.
Here is a snip from the parts catalog for your bike. The cap area water drain and the cap vent both "Y" into a single hose.
There are screw-in spigots with o-rings sealing them to the bottom of the tank where the 2 hoses attach.
Inside the tank are the molded tubes leading to the gas cap area. The cap itself is the vent system with a labyrinth that traps raw gas and a small rubber mushroom shaped seal that leads that labyrinth into the hose to atmosphere.
The o-ring seals could be leaking, swelling to seal while sitting and leaking again after heating from the engine running.

I would suggest you pull the tank off and inspect everything related. Unless your fuel pump plate is leaking (you're certain of that) then it must be related to the cap, internal molded hoses or the attachment to the tank for the external hoses.

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In that line of thinking maybe you are building pressure because your drain hose is party crimped and as the pressure increases from riding it finally pushes gas out. —arm chair pondering. 🤔
 

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Here are a couple of images to help you figure it out:

Tank Internals:

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The Evap Emissions Canister (If you have this, it lives low on the LEFT SIDE of the frame.):

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That bike wont have a Evap fitted on that year in the UK.

As said above, are you sure you don't have anything kinked from the tank. Take it off and check as its easy to trap something when refitting in the past.

My 2016 Dragster sometimes there is a bit of a smell after riding. I put this down to just venting. But its never leaked.
 

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Discussion Starter · #12 · (Edited)
Wow, thank you for all the replies and suggestions. Here's what I know so far and I'll try to carve some time over the weekend to get the tank off and do more investigation.

I would conduct an experiment to see if the level drains/returns to the same level each time the "overflow" occurs.
I haven't checked this yet but I know at the moment and with no leaks fuel is sitting just above the fuel filter, just below the airbox indent. It's too cold/frosty to take her out where I am, but will keep an eye next time I fill up.​

There are screw-in spigots with o-rings sealing them to the bottom of the tank where the 2 hoses attach.
Inside the tank are the molded tubes leading to the gas cap area. The cap itself is the vent system with a labyrinth that traps raw gas and a small rubber mushroom shaped seal that leads that labyrinth into the hose to atmosphere.
The o-ring seals could be leaking, swelling to seal while sitting and leaking again after heating from the engine running.

I would suggest you pull the tank off and inspect everything related. Unless your fuel pump plate is leaking (you're certain of that) then it must be related to the cap, internal molded hoses or the attachment to the tank for the external hoses.
Have you tried leaving the cap open after a ride to see if it’s pressure related?
I saw a post here (not sure if it was you or lee) where those mushroom seals were removed. I'm not intending to do that, but that and your reply gave me the idea to pull the cap apart for inspection and cleaning. I've tried to open the cap after a ride momentarily and then at few hours/days interval to equalise the pressure but that didn't stop the leak. I didn't leave the cap off for extended period of time as I was concerned about fire risk. The cap does hiss after a ride and there's a whoosh of air sucked into the tank when I open it, after a ride and even after the bike has cooled down, but I thought this is somewhat to be expected having seen some other posts.​

In that line of thinking maybe you are building pressure because your drain hose is party crimped and as the pressure increases from riding it finally pushes gas out. —arm chair pondering. 🤔
I think the blow test should've identified any kinks or crimps but I don't remember whether I did this when the engine was cold or hot. Another thing to try.​

That bike wont have a Evap fitted on that year in the UK.

As said above, are you sure you don't have anything kinked from the tank. Take it off and check as its easy to trap something when refitting in the past.

My 2016 Dragster sometimes there is a bit of a smell after riding. I put this down to just venting. But its never leaked.
Confirmed, no Evap - although my partner would tell you that I'm blind and miss obvious things (don't believe her!). Same comment as above on kinked pipes. The strong smell is what made me suspicious in the first place and then I found the pool of petrol!​
 

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Discussion Starter · #13 ·
Oh, and in a different post here someone was suggesting the fumes may condense in the cap or breather pipe and leak as fluid. I find it quite hard to believe this could cause anything more than a few drops. Any consensus from the forum?
 

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Your whoosh when opening the cap indicates pressure (or vacuum) build up inside the tank. The hissing sound should be coming from the hose...unless the cap can't vent and the seal to the tank is being broken by the pressure.
The "mushroom" seal prevents fuel leakage at the gas cap area if the bike falls over.
I think you cap vent hose is blocked. Not likely a problem inside the cap itself.
 

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Oh, and in a different post here someone was suggesting the fumes may condense in the cap or breather pipe and leak as fluid. I find it quite hard to believe this could cause anything more than a few drops. Any consensus from the forum?
Were this true, anyone living in a changing temperature climate would have fuel under their bikes......
 

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gave me the idea to pull the cap apart for inspection and cleaning
Be careful when you do this. If your cap is as the one I disassembled, then there are ball bearing check valves and springs in there.....they can shoot anywhere!
 

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Discussion Starter · #17 ·
Were this true, anyone living in a changing temperature climate would have fuel under their bikes......
My thoughts too. Inside the cap I saw a mist of condensed fuel on the metal part behind the outlet mushroom and that's as much as I would've expected.

Be careful when you do this. If your cap is as the one I disassembled, then there are ball bearing check valves and springs in there.....they can shoot anywhere!
Thanks for the heads up. I've done that many times, a 10 minute job taking 2 hours extra seatching for those little missing parts! Luckily not this time given the warning 😁
 

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Discussion Starter · #18 ·
I didn't get as far as taking the tank off but did a little more investigation.

Your whoosh when opening the cap indicates pressure (or vacuum) build up inside the tank. The hissing sound should be coming from the hose...unless the cap can't vent and the seal to the tank is being broken by the pressure.
I opened the cap and nothing out of ordinary there. The only thing I noticed was there was a little more resistance on the outlet mushroom compared to inlet which suggests the tank normally works under slightly raised pressure. This may justify the whoosh sound when opening the cap after a ride. I can get a weak whoosh by simply blowing into the breather valve underneath the bike.

I checked inside the tank with an inspection camera. Couldn't see any obvious cracks or disintegration on the 2 moulded pipes. Not to rule that out 100% as I couldn't reach certain areas and a hairline crack would be hard to see anyway. One thing I noticed, the inside of the tank looks like a teenager face full of pimples and uneven like shown. Is this normal?
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Finally I checked the external pipes visually and by touch. No kinks or cramps but I noticed the vent spigot under the tank was somewhat loose. This is #24 in the above diagram leading to pipe #10 and onto Y connector.

If I'm not mistaken, the moulded vent pipe is internally sealed to the tank and other than overflow no leak is expected here even if the spigot is loose. Is it so? In that case that cannot be the cause of the leak, right?

Thanks for all the help and suggestions so far.
 

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The tank does not operate under any pressure. It should be atmospheric pressure inside while running or parked.
I haven't looked inside a triple fuel tank, but all diagrams show connection spigots with o-ring seals screwing into the tank base.
 

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Discussion Starter · #20 ·
Actually, looking at the tank internals diagram that @silentservice703 posted, my assumption there seems incorrect and that may well be the source... looks like tank will come off tomorrow.

If someone can confirm please also tell me if the spigot can be tightened without opening the tank. If not, how can I drain the remaining fuel and do I have to replace any o-rings for example on the fuel pump assembly when removed.
 
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