SFC restoration question

C

Christian J

New member
Location
Boston, MA
two steps forward on getting a new-to-me '74 750 back on the road and one step back today. The fiberglass tank ( a reproduction) is weeping fuel at a seam.
I'd rather not put time & money into patching a repro tank only to have it fail again in a few years. Who will be supplying tanks for a 1974 bike in 2030? Good luck...
So, to fix it once and forever what tank do I source as a replacement? Wolfgang is my relatively local guy and he sells a nicely finished aluminum tank. It will need exterior paint. Is this the best option?
 
Not sure if carbon fibre tanks still available from Boba.
Ally is a good option if your running ethanol fuel,
Is probably why your tank is falling apart. Epoxy base laminates work with ethanol.
 
Did you put resin in it?
New fibreglass doesn't like unleaded fuel. Nothing to do with ethanol.
Always use resin before putting fuel in. ALWAYS.

Paul
 
It was Marnix who put me on to this, many years ago. When he restored his 5000 SFC with a fibreglass replica tank, it rapidly started playing up and he found full of orange goo in the 36mm Amals. Just unleaded on new fibreglass, no ethanol. Old fibreglass that is impregnated with fuel doesn't leak.
I had a fibreglass tank kindly donated by Boba when my SFC was vandalised.
The team who restored the bike apparently weren't aware of the problem, because they put fuel in the freshly painted tank, and it came through the fibreglass.
Always coat new fibreglass nowadays.

Paul
 
Don’t know what it was that made tanks dissolve at the time, may have been ethanol too. I remember seeing an original SFC tank dissolve after decades without issues. This happened simultaneously with my Rickman CR 750’s tank from 1974. Was pretty devastated..

Now it seems under control by applying Tank Cure epoxy, but I’m very picky with the fuel that I put in them.

I had a n original SFC fibreglass tank split due to a blocked air vent hole in the fuel cap. With the bike parked in the sun it split at the lower seam.. Tank Cure epoxy will take care of that too by the way.

Marnix
 
MarnixSFC said:
Don’t know what it was that made tanks dissolve at the time, may have been ethanol too. I remember seeing an original SFC tank dissolve after decades without issues. This happened simultaneously with my Rickman CR 750’s tank from 1974. Was pretty devastated..

Now it seems under control by applying Tank Cure epoxy, but I’m very picky with the fuel that I put in them.

I had a n original SFC fibreglass tank split due to a blocked air vent hole in the fuel cap. With the bike parked in the sun it split at the lower seam.. Tank Cure epoxy will take care of that too by the way.

Marnix
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Be assured Marnix, that fibreglass still dissolves today.
My original SFC tank was un-affected.

Paul
 
The second owner of my Pantah found the same sticky gunk in the carbs from the Shell Optimax with zero Ethanol he had recently decided to start using, more bang for buck adds on TV caused that choice, dissolving the 25litre replica Imoya fibreglass tank it had run successfully for at least 5 years previously. At the time this was a complete mystery as to what the hell was happening. He had unglued the slides a couple of times and then the tank just burst open one night. That was an expensive mistake, that TL lost the Imyla tank and Imoya seat and required a replacement TL tank and then subframe mods to accommodate an SL seat just because some chemist must have changed some volatile in THAT fuel back then.
 
Paul Marx said:
Be assured Marnix, that fibreglass still dissolves today.
My original SFC tank was un-affected.

Paul
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I am well aware of that, I have coatings in all my tanks, also the aluminium ones.
However, It’s still a good idea to use fuels that are ethanol free.

Marnix
 
MarnixSFC said:
I am well aware of that, I have coatings in all my tanks, also the aluminium ones.
However, It’s still a good idea to use fuels that are ethanol free.

Marnix
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I use what I can find in darkest France Marnix, and elsewhere.
I don't recommend resin in other than fibreglass. It turns repairing the dent you made, and we all dent our tanks some time, into a major operation since you need to get the resin out. I regret coating a couple of tanks a long time ago when it was fashionable. Fashionable like using fuel additives.

Paul
 
Hi, just done one with the same problem..the liner is a bitch to sand out where it has stuck on the rough surfaces,but did not stick to the smooth resin poured into the tank after assembly. This tank also leaked at the seam in a spot where the post assembly resin did not cover very well
 

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There are liners that have a good rep and some that don't. Do you have an idea what was used there? Application is also critical. My one and only attempt was CREME in a rusty steel triumph tank, and that was a complete disaster. That tank ended like your pics. Cut open and fixed 100% in the end.
 
Vince said:
There are liners that have a good rep and some that don't. Do you have an idea what was used there? Application is also critical. My one and only attempt was CREME in a rusty steel triumph tank, and that was a complete disaster. That tank ended like your pics. Cut open and fixed 100% in the end.
Click to expand...
Not sure of the product used but the tank is solid,no degradation of the tank. Pretty sure it's epoxy resin and the liner added where it didn't seal in one spot.
 
So far so good with my tank. Been using unleaded premium in all the years of using it in Oz, 86 to present, not sure what the fuel was in the UK back in 83-86 or what I used in the US in 82-83.
I would love to have brought one of Boba's carbon tanks when available. Have thought about making a mold from mine but being an original not prepared to risk it. Pretty sure Road and Race in NSW still sell fibreglass tanks for the disk brake models.
I would concider
If anybody has one [Oz based] and would be prepared for me to make a mold from it I'd supply a carbon fibre version for
your troubles.
The carbon tank I made for the motodd is still as good as the day I fitted it back in 2014.
 
sfc vintage said:
glasfiber is for Boat 😱😱🧐👍👍👍
Click to expand...
It's not even a particularly good material for boats. It suffers from osmotic blistering (AKA: boat pox) in salt water.
Not entirely sure what it is good for. Custom body panels maybe?

Most boat owners or builders have their favourite material for boats and reckon all others are rubbish for one reason or another (I'm a steel boat man).

I knew an old wooden boat builder (now deceased) who hated fibreglass. He referred to it, somewhat disparagingly, as "bandages and snot", often with an expletive or two added for good measure. He was a funny old bugger.
 
Vince said:
Application is also critical.
Click to expand...
So true, preparation and application are probably more important than the product used.
Another important factor is the quantity that you poor in. Due to its shape, an SFC tank is usually not fully covered with the sealing product, which usually is the reason for it to come loose with time.

Marnix
 
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Dellortoman said:
It's not even a particularly good material for boats. It suffers from osmotic blistering (AKA: boat pox) in salt water.
Not entirely sure what it is good for. Custom body panels maybe?

Most boat owners or builders have their favourite material for boats and reckon all others are rubbish for one reason or another (I'm a steel boat man).

I knew an old wooden boat builder (now deceased) who hated fibreglass. He referred to it, somewhat disparagingly, as "bandages and snot", often with an expletive or two added for good measure. He was a funny old bugger.
Click to expand...
Not really accurate, boats once blistered when they used a particular resin, particularly the old Uniflites, but that hasn’t been an issue for several decades. Mostly it was due to modifiers in the polyester resin such as fire retardants in the Uniflites. Epoxy and vinylester resins do not blister. Besides, blisters have never been a structural issue, they are purely cosmetic and always below the waterline.
 
motoddrob said:
So far so good with my tank. Been using unleaded premium in all the years of using it in Oz, 86 to present, not sure what the fuel was in the UK back in 83-86 or what I used in the US in 82-83.
I would love to have brought one of Boba's carbon tanks when available. Have thought about making a mold from mine but being an original not prepared to risk it. Pretty sure Road and Race in NSW still sell fibreglass tanks for the disk brake models.
I would concider
If anybody has one [Oz based] and would be prepared for me to make a mold from it I'd supply a carbon fibre version for
your troubles.
The carbon tank I made for the motodd is still as good as the day I fitted it back in 2014.
Click to expand...
I have a mold for sfc disk brake tank,fairing and bodywork. Made by Rod Pratt from Melbourne.
 
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