Fibre Glass Tanks

Hi Guys, Can you recommend a decent fibre glass tank sealer specifically to seal against the dreaded E10 Ethanol fuels??

I used Caswell. Seems fine 3 years later. Lots of threads on this subject here, though.

Your tank is polyester resin so best to use a 2 part type epoxy product (believe this is the Caswell formulation and maybe Por15) as that will have the best bonding characteristics. Epoxy is used extensively in the marine industry for permant repair on polyester structures b/c of its superior bonding ability to other resins.

The major issue here will be the 50+ yrs old inside surface with embedded contaminants. Ideally after thorough cleaning with degreasers and alcohol solvents, I'd suggest tumbling it a few hours with some abrasive ceramic beads or metallic nuts/bolts etc to try to rough up the insides, exposing fresh resin/glass fibre for the epoxy to form good secondary bonds to. I've heard folks wrapping tanks in duvet or foam blankets and putting a clothes dryer to tumble gently for hours to do this inside abrasion.

Move to the Isle of Man

I used Caswell in my '68 Ccommando tank. I can't remember exactly how long ago, but it's about ten years I think. It's still good now, but the important part is the prep. POR 15 is also very good, but only on steel tanks.

Martyn.

Buy an aluminium tank and rubber-mount it. Solves a lot of problems. - Do a cost/benefit analysis. - 'You cannot make silk purse out of a sow's ear'.
Is there anyone making aluminium Commando tanks which are exactly the same shapes as the original steel tanks ? You coulld paint one to look as though it was original equipment.
If you buy a steel tank from India, it will cost you money - 'quality does not cost - it pays' ?

Matchless said:

I used Caswell in my '68 Ccommando tank. I can't remember exactly how long ago, but it's about ten years I think. It's still good now, but the important part is the prep. POR 15 is also very good, but only on steel tanks.

Martyn.

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The POR15 kits are for steel tanks, but that is really applying only to the prep agents like the metal etch and degreaser components. I believe the actual sealer is still an epoxy resin so it should still work well if the glass tank is properly prepped.

acotrel said:

Buy an aluminium tank and rubber-mount it. Solves a lot of problems. - Do a cost/benefit analysis. - 'You cannot make silk purse out of a sow's ear'.
Is there anyone making aluminium Commando tanks which are exactly the same shapes as the original steel tanks ? You coulld paint one to look as though it was original equipment.

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Alloy tanks sure look sweet. Bonus is you save $500+ on a paint job. Question: were Commandos ever sold from dealers with alloy or raw steel tanks? Asking b/c my "Collector" status insurance policy requires the bike to be period correct in colour scheme and configuration.

Tornado said:

The POR15 kits are for steel tanks, but that is really applying only to the prep agents like the metal etch and degreaser components. I believe the actual sealer is still an epoxy resin so it should still work well if the glass tank is properly prepped.

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I would be interested to see if it works on steel. Has anyone tried it?

I can't ever recall seeing an aluminum or raw steel tank on a Norton at a dealership, never saw any brochures displaying them either. I was actively riding and breaking British bikes from 1968 through 1975 and then some. Maybe another member here will prove me wrong....

acotrel said:

Buy an aluminium tank and rubber-mount it. Solves a lot of problems. - Do a cost/benefit analysis. - 'You cannot make silk purse out of a sow's ear'.
Is there anyone making aluminium Commando tanks which are exactly the same shapes as the original steel tanks ? You coulld paint one to look as though it was original equipment.
If you buy a steel tank from India, it will cost you money - 'quality does not cost - it pays' ?

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Guys i have to come clean ... the fibre glass tank I'm looking to seal is on my Bultaco Sherpa T.... I'll head off to Coventry now

olympus said:

Guys i have to come clean ... the fibre glass tank I'm looking to seal is on my Bultaco Sherpa T.... I'll head off to Coventry now

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Do you mean it's one of those funny foreign motorcycles?

Another foreign interloper. I have a Morini Camel 500 with a fibre glass tank. I used Wyldes Flowliner 2 pack as recommended by @trident sam. It's not cheap but been in about 4 years now, no sign of any issues. (I gave it two coats to be sure).

Matchless said:

I used Caswell in my '68 Ccommando tank. I can't remember exactly how long,ago, but it's about ten years I think. It's still good now, but the important part is the prep. POR 15 is also very good, but only on steel tanks.

Martyn.

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I did a PR glassfiber tank with Caswell. I tried very hard to follow the instructions, but after a couple of years, it started to bubble up near the filler cap. As far as I can see with a camera probe, the resin formed a drip and seems to have had an air bubble, which seems to be the point of failure.
I now think the only way to be reasonably certain of full coverage is to cut the tank open, apply the Caswell over the whole inner surface & rejoin (using more Caswell resin as the glue. There was a longish thread on this several years ago.

I'm now the owner of an Indian made PR steel tank, which looks promising.

SteveBorland said:

I did a PR glassfiber tank with Caswell. I tried very hard to follow the instructions, but after a couple of years, it started to bubble up near the filler cap. As far as I can see with a camera probe, the resin formed a drip and seems to have had an air bubble, which seems to be the point of failure.
I now think the only way to be reasonably certain of full coverage is to cut the tank open, apply the Caswell over the whole inner surface & rejoin (using more Caswell resin as the glue. There was a longish thread on this several years ago.

I'm now the owner of an Indian made PR steel tank, which looks promising.

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Hi Steve

I went with a steel PR tank from Royal Choppers early on in my ‘73 Commando project. It was helpful to find threads like this before rolling the dice.

May I ask how your tank purchase went?

SteveBorland said:

I did a PR glassfiber tank with Caswell. I tried very hard to follow the instructions, but after a couple of years, it started to bubble up near the filler cap. As far as I can see with a camera probe, the resin formed a drip and seems to have had an air bubble, which seems to be the point of failure.
I now think the only way to be reasonably certain of full coverage is to cut the tank open, apply the Caswell over the whole inner surface & rejoin (using more Caswell resin as the glue. There was a longish thread on this several years ago.

I'm now the owner of an Indian made PR steel tank, which looks promising.

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I bought a second hand fibreglass fuel tank off eBay for £35 which had been epoxy lined but the lining was breaking up and coming out in chunks. I got out out all the loose pieces with long nosed pliers etc and then gave it the dry-wall screw treatment with various solvents for what seemed forever (neighbours must have thought I was a nut......). I then left the tank for several months before giving it the Caswell treatment and a pretty decent respray (if I say so myself). I put fuel in and all seemed good but the first time I really brimmed it bubbles slowly started to appear in the paint around the filler neck so I drained the petrol, left it for a week or more and then carefully applied Araldite Putty inside the tank all around the filler neck to make a fillet between the fibre glass and the metal filler tube - long fingers and some dexterity helps. I left it to harden for a week or two and have since brimmed the tank with no further bubbling. I was able to massage the original bubbles down with a smooth edged Letraset burnisher so they were virtually un-noticable and the paint has fortunately set hard again. I think the epoxy must have not quite sealed against the filler neck and petrol was able to wick up up through an absolutely miniscule gap. Note; I Caswelled the original tank about seven years ago when it sprang a leak overnight and it was then fine up until I swapped tanks four months ago - I wouldn't hesitate to recommend the Caswell treatment but I think preparation is key.

So as not to derail this thread I have started a new one. It would be great to get some feedback...

Tornado said:

Asking b/c my "Collector" status insurance policy requires the bike to be period correct in colour scheme and configuration.

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Lordy!! Never seen similar over here. Just photos and any listed mods/upgrades..

Tornado said:

Alloy tanks sure look sweet. Bonus is you save $500+ on a paint job. Question: were Commandos ever sold from dealers with alloy or raw steel tanks? Asking b/c my "Collector" status insurance policy requires the bike to be period correct in colour scheme and configuration.

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And what's particularly stupid about the motorcycle Collector plate in BC being so nit picky is that the vintage car guys, presumably because they're a larger lobby group, managed to negotiate a "Modified Collector" plate which pretty much allows dropping a '30s, '40s or '50s body on an '80s car and getting the full discount.

EstuaryBoy said:

Lordy!! Never seen similar over here. Just photos and any listed mods/upgrades..

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Though very significant $$$ reduction in insurance premium, there is a long, somewhat contradictory list of unacceptable items/conditions on the poorly worded form. For example period correct radio/stereos permitted but no "hidden" amplifiers. So I guess if it originally had an amp hidden in dash, boot that would have to be removed? Does being mount in the boot count as hidden? No purple dots on brake lamps?!? Apparently was a thing for some vintage cars to have done. So green dots are fine?

The marvels of bureaucracy never cease to amaze.