Implosion

[faffi]

Yesterday, on a hot (for Norway) day (27 Celsius), my son and I parked our 2009 V7 Classic and 2017 V9 Roamer respectively outside a shop to, well, shop. Refreshments. Bikes sat in the sun, as there was no shade to be found.

We refreshed ourselves and chatted for a good half hour, and when we finally went back to the bikes, I could smell fuel. Turned out to be a small puddle under my son's bike. I told him the pressure could have become high enough inside his black fuel tank to push a little fuel out the overflow. He decided to open the tank lid, and instantly two things happened: some fuel spat out around the lid, and the fuel tank visibly shrank. Never seen that before. Who came up with the idea of plastic fuel tanks

[bad Chad]

That's not an implosion, but I am knit picking.  Plastic tanks, seemed to have not worked out to well, as I don't think any major mfg is using them anymore?

[Fontain25]

Yeah I've seen it on Mules.Installed an accessory fuel vent and problem was diminished. Maybe illegal.

[PJPR01]

Check that your fuel vent line is not clogged…that’s where the vapors should be going.  A slight “whoosh” might be expected under extreme heat…but the most of the vapor should be venting.

[faffi]

Check that your fuel vent line is not clogged…that’s where the vapors should be going.  A slight “whoosh” might be expected under extreme heat…but the most of the vapor should be venting.

I will tell him this and ask that he checks.

[Vagrant]

That's not an implosion, but I am knit picking.  Plastic tanks, seemed to have not worked out to well, as I don't think any major mfg is using them anymore?

The v85 is.

[Vagrant]

This cap is vented and fits my v7III. Not sure about it fitting his.
https://www.amazon.com/dp/B08GMB3DV2?ref=ppx_yo2ov_dt_b_fed_asin_title

[s1120]

Do they have a rollover check valve in the vent? Ive seen those fail/stick causing overpressurization.

[jacksonracingcomau]

Sadly new gen people don’t understand fuel and temperature, most modern bikes don’t let you fill completely to compensate for idjits, This slipped past the keeper
Older generation already knew to fill after eating especially on hot day, caps used to vent all over your balls
Fill and ride, not park in hot sun, not rocket 🧬

[twowheeladdict]

Yesterday, on a hot (for Norway) day (27 Celsius), my son and I parked our 2009 V7 Classic and 2017 V9 Roamer respectively outside a shop to, well, shop. Refreshments. Bikes sat in the sun, as there was no shade to be found.

We refreshed ourselves and chatted for a good half hour, and when we finally went back to the bikes, I could smell fuel. Turned out to be a small puddle under my son's bike. I told him the pressure could have become high enough inside his black fuel tank to push a little fuel out the overflow. He decided to open the tank lid, and instantly two things happened: some fuel spat out around the lid, and the fuel tank visibly shrank. Never seen that before. Who came up with the idea of plastic fuel tanks

There was a recall on that generation V7 in the US.  Don't recall the specifics or whether the Euro bikes needed it, but it had to do with swelling tanks. 

[slowmover]

My 2010 V7 Classic got a giant raised bubble on it. Replaced under warranty.

[faffi]

Sadly new gen people don’t understand fuel and temperature, most modern bikes don’t let you fill completely to compensate for idjits, This slipped past the keeper
Older generation already knew to fill after eating especially on hot day, caps used to vent all over your balls
Fill and ride, not park in hot sun, not rocket 🧬

That was not the issue here, because we had ridden 50 miles since the tank was filled, but yes, I have seen many tanks overflowing when parked in the sun after filling.

[faffi]

Do they have a rollover check valve in the vent? Ive seen those fail/stick causing overpressurization.

He did tip over at a standstill last fall, so this is another reason to check the went.

[rocker59]

Yesterday, on a hot (for Norway) day (27 Celsius), my son and I parked our 2009 V7 Classic and 2017 V9 Roamer respectively outside a shop to, well, shop. Refreshments. Bikes sat in the sun, as there was no shade to be found.

We refreshed ourselves and chatted for a good half hour, and when we finally went back to the bikes, I could smell fuel. Turned out to be a small puddle under my son's bike. I told him the pressure could have become high enough inside his black fuel tank to push a little fuel out the overflow. He decided to open the tank lid, and instantly two things happened: some fuel spat out around the lid, and the fuel tank visibly shrank. Never seen that before. Who came up with the idea of plastic fuel tanks

Had you just filled up?  If you're going to park in the sun on a warm day, it's best to fill up AFTER your stop.

But yeah, sounds like the fuel tank vent is not working properly.  Check valve probably stuck.

And, it sounds like a replacement metal tank needs added to the wish list..

[jacksonracingcomau]

That was not the issue here, because we had ridden 50 miles since the tank was filled, but yes, I have seen many tanks overflowing when parked in the sun after filling.

Not calling you naive but I don’t know any other way of fuel pressure building up in PARKED petrol tank on hot day.
Black metal tanks do the same thing quicksmart. White is good for obvious reasons

FWIW I have the exact same plastic tank on my Lario, ex “Racer” , chrome fell off, I love the look even if original owner didn’t. I drilled for fuel taps, removed pump and got rid of silly neck that stops you filling it up. I use a 3” flush filler cap and get 18 ltres in (factory rated 16?).
The pressure release / breathing vent is on the underside of tank left side, I fitted an additional valve as release was  not high enough pressure, it would spit when full, even cold. Now it never leaks a drop, of course I never park in sun when full, actually never park it full at all, old habits die hard.

That plastic tank works for me, can’t dent or scratch it, lovely shape, I have another I totally covered in rooskin, hangs on my wall but will see action one day, probably on carb bike again but could go on Roamer .

[SIR REAL ED]

Definitely sounds like a non-functional gas tank vent.  I have no knowledge if any "vapor trapping," emissions control hardware is on that bike.

Plastic tanks swelling as they get hot is normal.  Lots of solid and liquids expand with a temperature increase. 

Pressure building inside the tank should not happen.

If you have an in-tank fuel pump, perhaps the high pressure side of the pump is leaking and pressurizing the tank?

I like the idea of plastic tanks, until a problem occurs.  Oddly enough, I think the same of metal tanks......

[faffi]

Not calling you naive.

You sure? 

Anyway, I presume the pressure plus raising vapor must have cause fuel to climb to the top of the tank and then dribbled down. We are not talking much fluid, but enough to make a stain and cause the smell of petrol. The spray out the lid as the tank was opened suggest to me fuel vapor was sitting just below the lid at the moment, despite the tank lacking about 3 liters from full.

[jacksonracingcomau]

You sure? 

Anyway, I presume the pressure plus raising vapor must have cause fuel to climb to the top of the tank and then dribbled down. We are not talking much fluid, but enough to make a stain and cause the smell of petrol. The spray out the lid as the tank was opened suggest to me fuel vapor was sitting just below the lid at the moment, despite the tank lacking about 3 liters from full.

Cool, physics lesson learned
Everybody had to learn this in the days of carbs and fuel caps that vented to atmosphere, first hot day, they stink and dribble. Exactly why all my old bikes have flush fillers and one way vent valves.

Of course modern bikes use charcoal canister on this vent, you could retrofit one if it bothers you. Absorbs the smell, only leaks if it’s full. Elf and safety and all that, perhaps necessary when people don’t know about heat and petrol

[SIR REAL ED]

Cool, physics lesson learned

Excellent campfire Physics!

Temperature increase cause expansion of air and fuel in tank, which would increase pressure, while pressure is theoretically simultaneously being reduced by fuel consumption and increase in tank volume due to thermal expansion.

My previous speculation of a leak on the high pressure side of the pump is BS.  No change in fuel volume inside the tank due to pump function.

So, when you are riding in the rain, do you ride faster to get home sooner, or ride slower and get hit with less raindrops per minute for a longer period of time?

Great campfire camaraderie:

https://www.youtube.com/watch?v=VPIP9KXdmO0

[Dr. Enzo Toma]

Years ago on a Cagiva climbing Monarch Pass (11,312 ft / 3,448 m) I found the bike pouring fuel out the overflow at the summit. Silly me went to burp the fuel tank and was treated with a geyser of boiling fuel from an already half empty tank. Never underestimate the impact of a reduction in atmospheric pressure! Luckily I only needed to go downhill for a while after that as there wasn't much fuel left.

[SIR REAL ED]

Years ago on a Cagiva climbing Monarch Pass (11,312 ft / 3,448 m) I found the bike pouring fuel out the overflow at the summit. Silly me went to burp the fuel tank and was treated with a geyser of boiling fuel from an already half empty tank. Never underestimate the impact of a reduction in atmospheric pressure! Luckily I only needed to go downhill for a while after that as there wasn't much fuel left.

That is an excellent lesson to share.  Thanks.