Gas leaking from under the cap

[Ducati Scotty]

+1, not a drop.

[hillntx]

Where do you find the cork gaskets?

[WillW]

You have to make your own. 2mm cork sheet from a craft supplier.

[Lwt Big Cheese]

A petrol cap gasket is another item I don't have!

And yes it does leak.

And an MOT failure. Or so I'm told by the tester when he handed me a pass certificate for £20.

 .

[barenekd]

The screw on gas caps (actually Triumph caps) the California bikes have seal quite tightly. Usually they don't leak in any position.
Bare

[idk]

The cork gasket looks like a good idea. Do you need to soak them? 

[Ducati Scotty]

The local auto shop should have sheets if fuel resistant cork gasket sheet for a modest price.  Cut to size, no presoak required.

Scott

[Kevin Mahoney]

All petrol caps EXCEPT the CA screw on caps are vented at the cap to allow fuel flow.
This may or may not be part of what some of you are seeing. The CA caps are sealed to prevent HC from escaping from the tanks. CA is the only place in the world with this requirement and I am surprised. These tanks are vented into a canister with activated charcoal in them. The charcoal absorbs the vapors. When the bike runs it draws a small amount of air through the canister which purges it. There are no negative performance problems with it. They look unsightly but  that can be improved upon. For my money it is a good device.

[singhg5]

Some riders had mentioned that their Cork Gaskets swell up or became mushy.  Just beware to find the right material.

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This is from an old Post "Do it yourself Gas Cap Gasket"
bullethead63
 Grand Gearhead
 Posts: 696
Re: Do it yourself Gas Cap Gasket (or Petrol Cap, if you wanna be fancy)
« Reply #10 on: November 04, 2010, 10:18:11 AM »
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After about a week,my new gasket has gotten a little mushy,and swollen...if you're going to use one of these for a petrol tank cap,keep a spare in your tool box,and switch them out with every fill up...that's what I had to do this morning...

walken4life
 Scooter
 Posts: 50
Re: Do it yourself Gas Cap Gasket (or Petrol Cap, if you wanna be fancy)
« Reply #11 on: November 05, 2010, 08:40:25 AM »
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That's sad.  Mine seemed ok last fillup but I will check it again when I do the final fill up before winter storage in the next few days.  Thanks for the update.
« Last Edit: November 14, 2010, 08:02:45 AM by walken4life »

Updates:
My home-made gasket from above swelled a bit .

Decided to try making another gasket with a new material.

[Ducati Scotty]

+1.  That's why you should look for fuel resistant cork gasket material at an auto shop, not craft supply stuff.  A whole roll cost me about $6 I think.  Same goes for the o-ring solution, fuel resistant or it will turn to mush.

Scott

[singhg5]

Same goes for the o-ring solution, fuel resistant or it will turn to mush.

The stability of o-rings against water, salt, gasoline, oils and temperature depends on the material used to make them as shown in the chart below.

[WillW]

I use plain old 2mm cork sheet which I buy in bulk (for my business) from the sawmill. It works fine. I did grease it at first, but only the once, and it's still good after a year or so. Perhaps it just happens to be gasket grade - it's fairly dense. I have seen some poorer quality stuff around, so I guess that'll be the craft shop stuff.

[Arizoni]

Singhg5
The chart in your post is excellent!

A few words about some of the elastomers mentioned in it if I may.

Although some of the colors of these materials are the same, the colors can indicate if you've got the right material for others.
There are no hard and fast rules about these colors so use them as a general guide.

For instance, Silicone, which is very poor with gasoline is usually orange.
Fluoro-silicone, which is excellent with gasoline is usually blue
European Viton is usually green but American Viton is usually brown.
Buna-N (Nitrile) is often gray
Neoprene is usually black
Color Kalrez (Perfluoroelastomer) EXPENSIVE.  It is so expensive that we used it in jet engines only when nothing else would do.

[Rich Mintz]

On my 2010 Bullet C5 (with under 1000 miles), I smell gas fumes more often than I anticipated.

And I had this happen: I filled the tank at night in cold winter weather, then parked the bike on the side stand in a warm garage. Overnight, due to expansion, gas dribbled over the side onto the floor.

I did the math http://richmintz.com/2013/01/in-which-i-almost-blow-up-a-square-block-of-lower-manhattan/ and it looks like 3 gallons of gas can expand on the order of 30 cubic inches with that kind of temperature rise -- that seems implausible but even if that's 3X the real answer, it still explains where the gas came from. Even with a tight seal, I would have had leakage, and I know empirically that I don't have a tight seal.
 
Since then, in the warm garage I always park on the center stand. And I ordered a roll of "cork gasket material" from an Amazon vendor, which came last night -- when the snow clears, I'll cut a ring of it out and try it in the tank.

[singhg5]

Made cork gasket and it helped a lot -

http://www.youtube.com/watch?v=4qtAOoKsvq8