Hi Guys,
Ever since I have had the bike, after a medium/long ride when its hot, I have a hissing noise coming from the fuel cap. When I open the cap, pressure is released and all is good.
Is this fairly normal or do I have a blocked fuel vent somewhere?

Normal

Mine will whistle...my 07 had it BAD.The 2012,2013...not too much.

Yannih, think basic science. Cool contracts, heat expands and the constant is the Penultimate number. Inside the tank sits the penultimate. The partial empty tank warms up that air bubble inside as the ambient rises during the hours of the day. So when you hear the whoosh out the tank cap, the tank spring pressure is set at 14.7 for argument sake; the air expands and over pressurizes the tank; the spring collapses; releases the rubber diaphragm to begin flapping out the expansion like a whoopee cushion.

So if the penultimate can push that spring open, then it can 'for every action.' To seal the vapors from escaping thru the cap, they have a matching diaphragm sitting up and one sitting down. As the gas leaves the tank, the tank either implodes itself or your bike shuts off, whichever comes first, or pulls the diaphragm away from the escape side.

That's basically it, clear as mud, yes?

Understood Hub, but it seems a strange design to release the pressure through the fuel filling cap and have that hissing and whistling noise till things cool down?
No other bike I know of does this.
There must be a better way.

But as long as its normal I guess it's all good.

I was worried it was just my bike...

* Last updated by: yannih on 1/31/2015 @ 5:06 AM *

Character my man...character;)

Another swing and a miss from Hub.

Yan-man has a tank snake... highly venomous. I recommend you call animal control.

Well he is in Austrailia. They do have a lot of snakes!

Every ZX-10R and now the 14R has done that. I think even my SV650 did it. Your bikes talk to you. Enjoy the conversation. ;)

No other bike I know of does this.

I can only imagine the engine boot cutouts were reused; ninja sliced thin; ;then placed under the tongue for QC; onto the the tank cap assembly; the assembler grabs a tiny puck about this side of onion paper; slips it under the spring and cup so the spring does not dig into it;

Yo,Hag...Doesn't look like yer beastie there thought yer answer was too funny;)

I read every post on here to her in the evening.

Everytime I say "penultimate" the Queen Bee makes that face and growls.

Is this fairly normal or do I have a blocked fuel vent somewhere?

Normal. I switched to a LightTech cap which does not have the vent hole. No more hissing. Been so long, I forgot about it. I guess it must be the LightTech. I have a new Chinese cap and it also lacks the vent. IDK if some aftermarket caps have those. The EvoTech I have for my busa seems to have one. There's a little yellow hose that goes in there--I haven't installed it yet. Maybe the aftermarket cap makers consider the ventless design an improvement fpr the 14 since so many people have the hot hiss.

LightTech cap which does not have the vent hole. I have a new Chinese cap and it also lacks the vent.

I don't think they said one way or other but I never plugged mine so i guess they're open.

my 2c

my aftermarket cap for my gen 1 came with no vents, or instructions. left the vent holes open. hissing went away and it seals as its supposed to.
question (purely for interest sake) is there a difference between the Cali version and others as far as vents go? i had a Cali version with the fuel separator/vapor control under the seat.

My 14R funny enough doesn't hiss it sort of "whines/buzzes" as soon as you open the cap it goes away. how ever it goes away if you leave it as well.

untamed, cali has 3 vents, 48 state has 2 vents. Eliminate the weather/spillover vent tube and say we have 2 left. One is for air recover, the other is a liquid recovery. Use vacuum off 3 and 4 cylinders and you can use a suck to pump both vapor and liquid out to the other sucking cylinder. The only recover for a 48 state is vapor. Add the rain vent and the 48 state uses 2 vents.

Take your non-vented gas cap and shake it. If the bike tips over that stops it from pouring out. This is basic diagnosis:

1. Vent cap
2. Petcock flow
3. Kinked line to carbs.

Now fuel injection:
1. Gas cap venting
2. Fuel pump running and stopping
3. Kinked line to injectors.

There has to be a vent in the gas cap for flow, the cap housing, some way to stop flow upon tipover at the cap. This is still the gravity diagnostic tree out the petcock and out the fuel pump. You pop the cap off, that is not enough pressure to set the party noise making noise the 'dog face' has been met.

Yan-man has a tank snake... highly venomous. I recommend you call animal control.

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They have some hellacious bad ass spiders over in OZ too. I think he should stick his finger in the tank and wiggle it around. If nothing horribly poisonous bites it, he's good to go.

Mad

The spiders and snakes arent so bad here.
You stay out of their way and they stay out of yours.
But they do tend to get a bit angry if you screw with them...
Thats why if there is the slightest chance any of them are residing in my tank, my finger will not go anywhere near that fuel cap opening.

That's why we have wives...

* Last updated by: yannih on 2/2/2015 @ 12:21 PM *

make sure you don't have one of these lil buggers.

Aha! The fairing snake... rare and deadly!

Aha! The fairing snake... rare and deadly!

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Almost as bad as the Trouser Snake!!!

Mad

That poor little harnless snake probably had a fair distance to slither back to tell his mates about his 200km/h experience!

* Last updated by: yannih on 2/8/2015 @ 3:03 AM *

My '07 did it, especially on a hot day. The hotter the outside temp, the more pressure builds inside, waiting to be released.
I bought an aftermarket cap and the hissing is much less, but the hissing was never a concern for me.