Honda-SOHC

SOHC.co.uk Forums => CB500/550 => Topic started by: florence on September 05, 2025, 06:16:57 PM

Title: Fuel tank gasket
Post by: florence on September 05, 2025, 06:16:57 PM
Last week I fitted a new gasket on my fuel tank lid and despite it being ethanol proof, I don’t think it is thick enough.  Today I filled my tank, but when I got home noticed my trousers were doused with petrol. 

Does anyone recommend a good replacement, preferably ethanol safe.

Glad I’m no longer a smoker!
Title: Re: Fuel tank gasket
Post by: Nurse Julie on September 05, 2025, 09:09:04 PM
We use the original Honda ones on all our bikes, I also sell them on my Ebay page and they don't leak Florence. Is the one you bought OEM?
Title: Re: Fuel tank gasket
Post by: Oddjob on September 06, 2025, 11:21:27 AM
The fuel cap gasket can be a bitch to fit correctly as it has to go around both discs which ch live under there. Getting them both in can be difficult. If only the bottom is inside the gasket lip the fuel will leak past. If it feels loose or spins easily it not fitted right.
Title: Re: Fuel tank gasket
Post by: Oddjob on September 06, 2025, 11:28:53 AM
Sorry there are 3 discs not 2 and there is another gasket under the bottom disc which goes around the outside if the second disc, if that’s perished you need a new cap or a replacement off another cap.

I did a mod on the cap to remove the inner part and seperate it for zinc plating, which is how I know.
Title: Re: Fuel tank gasket
Post by: florence on September 09, 2025, 04:05:44 PM
Does anyone have a link to a diagram because I didn’t know there was more than one seal whic goes either side of the metal disk
Title: Re: Fuel tank gasket
Post by: deltarider on September 09, 2025, 06:59:35 PM
I know it is difficult to fit one. That's why I won't. My tank vents very well. ;D
Title: Re: Fuel tank gasket
Post by: DomP on September 09, 2025, 08:58:50 PM
Are we talking about the same cap as is fitted to a 550f?
Title: Re: Fuel tank gasket
Post by: Oddjob on September 10, 2025, 10:55:25 AM
No the F has a different cap Dom.

The easiest way to fit the gasket is to remove the inner part from the outer chrome shell, look inside and you’ll see 4 pointed pieces of metal holding it in. Just get a screwdriver under a couple of them and bend them up a little, the inners come out if 2 are bent normally. Fit the gasket, bend the prongs back to shape and refit.

You can clean up the rust on the underside of the cap at the same time. Maybe paint it to stop it reoccurring.
Title: Re: Fuel tank gasket
Post by: DomP on September 10, 2025, 10:46:32 PM
Firstly, so good to hear from you Ken!  I hope you are feeling better by the day.  That puts my mind at rest as mine was easy to fit
Title: Re: Fuel tank gasket
Post by: Oddjob on September 10, 2025, 11:59:50 PM
Getting a little stronger each day Dom. Will be next year though I’m ready to ride a bike again I reckon. Walking with crutches now but tire easily, about 30 yards is my limit at the moment.
Title: Re: Fuel tank gasket
Post by: Johnny4428 on September 11, 2025, 10:47:11 AM
Getting a little stronger each day Dom. Will be next year though I’m ready to ride a bike again I reckon. Walking with crutches now but tire easily, about 30 yards is my limit at the moment.
👍 glad to hear you are gradually improving Ken.
Title: Re: Fuel tank gasket
Post by: Laverda Dave on September 11, 2025, 11:27:19 AM
That's remarkable progress Ken considering how you were a few ago👍
Title: Re: Fuel tank gasket
Post by: DomP on September 11, 2025, 06:28:07 PM
Glad to hear that Ken!
Title: Re: Fuel tank gasket
Post by: florence on September 15, 2025, 12:23:42 PM
We use the original Honda ones on all our bikes, I also sell them on my Ebay page and they don't leak Florence. Is the one you bought OEM?

Hi Julie, great idea and thank you, I have ordered one from your site.

Title: Re: Fuel tank gasket
Post by: Nurse Julie on September 15, 2025, 02:10:12 PM
We use the original Honda ones on all our bikes, I also sell them on my Ebay page and they don't leak Florence. Is the one you bought OEM?

Hi Julie, great idea and thank you, I have ordered one from your site.
Thanks Florence, will dispatch later in week when back in UK.
Title: Re: Fuel tank gasket
Post by: florence on September 15, 2025, 02:24:33 PM
no rush and thanks again.
Title: Re: Fuel tank gasket
Post by: Murf on September 21, 2025, 09:02:50 AM
Useful post
my 75 K1 tank cap needs a new seal, I bought one some time ago but never fitted it as I couldn’t see how it could fit in and couldn’t see how the inside bit could be removed.
 I kept meaning to ask about it but when it became obvious the bike needed a lot of other work it got pushed down the list. I will have a look today while it’s fresh in my mind.
Title: Re: Fuel tank gasket
Post by: Oddjob on September 21, 2025, 12:28:57 PM
http://forums.sohc4.net/index.php/topic,195787.msg2302322.html#msg2302322

That thread may prove useful for anyone looking to restore a fuel cap.