Fuel resistant adhesive/sealant?

[FulmenParticipant @fulmen]

My ol’ Suzuki has developed a leak in the fuel cock. The hose nipples are fixed to the main body with a cylindrical fitting that has become loose over time.  There isn’t any signs of sealants or gaskets so I’m assuming it was originally just press fit, but obviously that’s no longer good enough. The material seems to be zinc based, new or even used replacements are unobtanium, so I have to work with what I’ve got.

I’m thinking epoxy but perhaps there are better products available for a reasonable cost?

[bernard towersParticipant @bernardtowers37738]

Any chance of using JB Weld?

[gerry maddenParticipant @gerrymadden53711]

Epoxy glues are destructively attacked by ethanol in the fuel so not advisable.

Gerry

[Gerard O’TooleParticipant @gerardotoole60348]

ANy chance of a photograph?

My old Honda came with the new, non OEM fuel tap which might have been from a later model.   I assume the  original had started to leak. Is there a possibility of just changing the fuel cock for one from a later bike.

[FulmenParticipant @fulmen]

There isn’t much room for anything except a bespoke part, and if there are other parts that will fit I have no idea how to find them.

[Robert Atkinson 2Participant @robertatkinson2]

Araldite rapid is reasonably resistant to petrol and ethanol. Assuming you are using it primarily as a sealant rather than as a structural adhesive it will work OK for your application.

However if you need to get sealant into a narrow joint that has come loose but cannot be dissassembled fully I’d suggest Loctite 270. This is thin enough to gat into a joint and if fuel and ethanol resistant.
https://docs.rs-online.com/b036/0900766b80076b82.pdf

Robert.

Edit I was typing when photo posted. Definetely a job for loctite . 270 or 641

[JasonBModerator @jasonb]

Plenty of people putting model fuel tanks together with JB Weld (original) including me so that would be my choice.

[FulmenParticipant @fulmen]

After seeing the data sheet for loctite it seems to be a very good fit (95% @ 5000h). As it is right now it’s more or less a tight slip fit, so there isn’t much space to fill. Not sure if epoxy will work well under those conditions.

 

[FulmenParticipant @fulmen]

I believe I have 641 in the shop, if not I can get 577 which is a sealant that looks even better:

https://datasheets.tdx.henkel.com/LOCTITE-577-en_GL.pdf

[Robert Atkinson 2Participant @robertatkinson2]

577 may be a bit thick if the parts are a close fit.
If you have an activator its worth using it on these light alloy parts.

Robert.

[FulmenParticipant @fulmen]

I can adjust the fit with a bit of emery, so that’s not an issue. I don’t see any minimum gap mentioned in the TDS, but I’ll try to get at least 0,05mm clearance. As for activators I really don’t like or trust them. From what I have read they reduce curing time at the cost of reduced strength on most materials. But I’m sure they have their role or they wouldn’t make them.

[Fulmen]

On 12 May 2025 at 15:36 Fulmen Said:

My ol’ Suzuki has developed a leak in the fuel cock. The hose nipples are fixed to the main body with a cylindrical fitting that has become loose over time.  There isn’t any signs of sealants or gaskets so I’m assuming it was originally just press fit, but obviously that’s no longer good enough. The material seems to be zinc based, new or even used replacements are unobtanium, so I have to work with what I’ve got.

I’m thinking epoxy but perhaps there are better products available for a reasonable cost?

No mainstream manufacturer would design or make a fuel fitting as a press fit.

Try this website for legacy Suzuki parts.

https://www.classicsuzukiparts.nl/en#

Or this site for good used parts.

https://www.baboon.eu/en/parts

Forget the “baboon” name it was originally “boonstra” but suffered from an attack of “web marketing”

I have had used stuff from them and it’s top class,  set of 4 nearly new throttle bodies for a Yamaha FJR 1300 for €70 ain’t too shabby, what you see on the website image they will ship it to you, they are dead straight.

[howardb]

On howardb Said:

No mainstream manufacturer would design or make a fuel fitting as a press fit.

You’re probably right, but it doesn’t change anything. The nipples are loose and leaking and will need fixing.

And thanks for the links, they didn’t have the fuel cock either but I’ll bookmark them for future reference.

 

[howardb]

On howardb Said:

On 12 May 2025 at 15:36 Fulmen Said:

My ol’ Suzuki has developed a leak in the fuel cock. The hose nipples are fixed to the main body with a cylindrical fitting that has become loose over time.  […] No mainstream manufacturer would design or make a fuel fitting as a press fit. […]

I suspect that this is actually the same situation that occurred with the carburettor on the V6 Ford Essex engine in the mid 1960s the fitting wasn’t a press-fit, it was cast-in.

The results of the failure were spectacular … notably in the Reliant Scimitar.

MichaelG.

.

Ref.

https://www.pistonheads.com/gassing/topic.asp?h=0&f=66&t=1986742

[Adrian R2Participant @adrianr2]

Is there enough meat on the main body to add a small lateral grub screw as a mechanical retention, still using loctite for the seal?

Motorbikes are at least easier to exit from in the event of a conflagration, but keep a fire extinguisher handy if starting in your garage.

[Adrian R2]

On Adrian R2 Said:

Is there enough meat on the main body to add a small lateral grub screw as a mechanical retention, still using loctite for the seal?

[…]

The more discreet version of the Weber fix was to use a slim taper-pin … but I used a self-tapper.

MichaelG.

[Michael Gilligan]

On Michael Gilligan Said:

 

I suspect that this is actually the same situation that occurred with the carburettor on the V6 Ford Essex engine in the mid 1960s the fitting wasn’t a press-fit, it was cast-in.

The results of the failure were spectacular … notably in the Reliant Scimitar.

MichaelG.

.

Ref.

https://www.pistonheads.com/gassing/topic.asp?h=0&f=66&t=1986742

Yes, saw one a few years ago and the resulting fire definitely took no prisoners.

[JasonB]

On JasonB Said:

Plenty of people putting model fuel tanks together with JB Weld (original) including me so that would be my choice.

Is that wise?  Big fuel tanks are more challenging than small and a model sized seal may not scale up safely.

Relying on experience is unwise for another reason: petrol varies, and it’s hard to know what’s in it.   The mix of light hydrocarbons changes, maybe with some aromatics like Benzine.  Plus there are many additives like Ethanol, Methanol, dyes, detergents, and anti-coking chemicals.  What worked last year may be iffy today.  Older vehicles designed for Leaded Petrol often used plastics and synthetic rubbers that are attacked by alcohols; not a problem then, it is now.

I don’t see significant risk in using standard JB Weld on a model fuel tank, but that doesn’t prove it’s suitable for motor bikes and up.  And there’s no need to risk it. As JB Weld sell a version specifically formulated to seal fuel tanks, it would be my choice!

Dave

 

[Michael GilliganParticipant @michaelgilligan61133]

Presuming [as I think one reasonably might] that the failure-mode is as per the Weber carb. … the clearance between the components will be tiny !

Loctite 638 or whatever, plus a pin or screw, seems the way to go.

MichaelG.

[JasonBModerator @jasonb]

The fuel tank stuff is in a stick form and far too thick to use in this application, Having now seen more details of the joint even the original may be a bit too thick. But it is also listed as fuel resistant just like JBWeld original on the makers sites so Dave why do you doubt one and not the other?

As for scaling up the part is not a fuel tank but a fitting which is actually smaller than many a model tank but of similar size to bosses, endcaps, etc that are fitted to model tanks so I fail to see the comment about scaling up having an effect.

[Howard LewisParticipant @howardlewis46836]

Anaerobic sealants work best with just a thou or two clearance, (0.025 0.05 mm), so if the connection is a slip fit onto the body, my inclination would be ensure that both fitting and bore are clean, apply Loctite, rotating to ensure complete coverage, and leave to cure for several hours.

Howard

[FulmenParticipant @fulmen]

Re: cast in: Interesting idea bit I don’t think so. Both parts are pot metal and the bore has a tapered bottom that does not correspond to the end of the nipple. Besides the nipples are 90° so you can’t insert a pin to create the bore.

I have considered a pin or grub screw, I’ll give it a go with the Loctite 577 first and see how it fares. Annoying to pay almost 30eur for 3 drops, but it’s still cheaper then a fire.

[Robert Atkinson 2Participant @robertatkinson2]

Fulmen,
I really would not use 577 especially if you have to buy some in. Your 641 is just as good as the gap is small. We had trouble with 577 on even fairly coarse parallel threaded fittings. It’s good for tapered fittings.
Note that it is so thick that it comes in a concertina bottle because it does not flow.

Robert.

[Michael Gilligan]

On Michael Gilligan Said:

On howardb Said:

On 12 May 2025 at 15:36 Fulmen Said:

My ol’ Suzuki has developed a leak in the fuel cock. The hose nipples are fixed to the main body with a cylindrical fitting that has become loose over time.  […] No mainstream manufacturer would design or make a fuel fitting as a press fit. […]

I suspect that this is actually the same situation that occurred with the carburettor on the V6 Ford Essex engine in the mid 1960s the fitting wasn’t a press-fit, it was cast-in.

The results of the failure were spectacular … notably in the Reliant Scimitar.

MichaelG.

.

Ref.

https://www.pistonheads.com/gassing/topic.asp?h=0&f=66&t=1986742

Also the Ford V4 fitted in later SAAB 95/96. Used to have one in the 80’s. some years later (1997) I saw one at the side of the road with the bonnet up and a guy in a tux looking in. I turned around at the next roundabout and as I pulled up behind him he had got back in and flames errupted!
I garabbed my extinguisher and put it out. I had tools etc in the car so was able to stick the brass tube back in with a Loctite methacrylate adhesive (330) and get him off to his evening do.
A prticular problem with V engines when stationary because the V traps the fuel vapour until it finds an ignition source.

Robert.

[FulmenParticipant @fulmen]

@Robert: Too late, it’s already glued, reassembled and filled with gas. Checked the glue after 30 minutes and I could not move them by hand, I’ll let it stand with petrol for a few hours before calling it.

Thanks for the help everybody.

[Author]

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