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Ethanol and fuel tanks.

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I have been restoring a Montesa Cota 348 Malcolm Rathmell Replica over the last few months, unfortunately although the tank/seat unit looked very good the dreaded Ethanol has attacked the inside even though it had been treated with a sealer ( make unknown). Great lumps of the stuff could be heard rattling around inside when the tank was shaken, after fishing as much out as possible ( depressing work) I realised that the only really effective repair would be either an alloy tank beneath a shelter or a complete alloy tank and seat unit both of which were turning out to be expensive options. I set the unit to one side and pondered my next course of action.

Fate played an Ace for me when I took some friends to visit Adrian Walkers Spinning Wheel Classic Cars  in Dronfield near to Sheffield  and Chesterfield. Apart from seeing plenty of bikes both road and competition based I saw sitting on top of an arcade machine a beautiful red glass fibre fuel tank. Can I touch this I asked Adrian, no problem he replied I’ve just had that made. It was to say the least an outstanding piece of workmanship. The underside was as good as the topside, there was no sign that it was fibre glass no mat no smearing just perfect. I removed the filler cap and peered inside, incredible there was no mat or strands evident. Who made this I asked and was shown an invoice for the tank. I made a note of the maker and the following day I made contact enquiring if he could make me a new seat and tank unit. Well I haven’t got a mould for that but I could make one. Will the Rathmell signature show on the new product, yes was the reply. Please go ahead. 

If you are looking at having a new Ethanol resistant fibre glass tank made for your bike then Roger Ennis is the go to man. This is not a sales patter and I hope that the moderator approves. Rogers been making fibre glass tanks etc for years and knows his stuff, a very entertaining and interesting person to talk to. I have asked his permission to pass on his telephone number which is 01594 562361. 🙂👍

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Did he use your original tank to make the mould? I won't ask the price, but did it turn out cheaper or at least competitive to an alloy one?

Edited by faussy

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Interesting. Montesa used a petroleum-safe-forever glassfibre..... At least safe for 40 years or so

 

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Hi Carl, petroleum safe it is but they didn't look into the crystal ball to see that petroleum companies would be removing lead and adding ethanol.

I asked Aral, here in Germany, what fuel they could recommend for old bikes with GFK tanks. Their answer was to use Ultimate 102, it has not ethanol or other GFK aggresive additives. The same would probably apply for all of the high octane products available such as Shell V power etc, but would need to be checked with the company concerned for the product/s in question.

I have the same problems as Section Swept with a 348 and a 247 at present.

Phil

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11 hours ago, faussy said:

Did he use your original tank to make the mould? I won't ask the price, but did it turn out cheaper or at least competitive to an alloy one?

Hi faussy,

All I can say is the price is extremely good. Yes the maker is producing a mould from my original tank, pretty much how most people go. The exception here is that I  asked for reinforcement in the seat and side panel areas. 

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6 hours ago, carl ekblom said:

Interesting. Montesa used a petroleum-safe-forever glassfibre..... At least safe for 40 years or so

 

You are probably correct but that was 40 years ago and environmental issues have seen the petroleum producers changing the formulas to the detriment of many things including fibre glass. As a previous owner of a few fibre glass boats you rapidly learn a lot about the construction and materials used. Therefore you find out that fibre glass and its gel coat are not waterproof and will absorb water over time, hence the dreaded lift out and drying out time usually every year or two depending on how affluent you are😳 Petrol or any liquid will be absorbed in a bikes GRP tank if left in for long periods. My Montesa tank had what us boaters call Osmosis that is bubbling of the sides of the tank, a paint specialist friend reckoned it could be micro blistering of the paint finish, the tank had been repainted at some stage in its life. A quick test with a pin proved that it was ethanol attack, the strange thing is that the base of the tank was clear of any bubbling; but then there was no gel coat applied in this area🤔 So some bright spark petro-chemist decided that ethanol would be good to reduce petrols environmental impact....without considering some of the potential issues.   

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You don't realize how much abuse the side of a tank can get from your knees. It can develop unseen cracks, then eventually leak. My 348 had that problem.

Edited by oldtrialer
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Has anybody tried  removing the ethanol from the petrol before use, as an alternative to sealants etc  ? 

there was at least one company selling a kit     { Ethanil.co.uk , I think was one ? }

I remember reading an article where you added a certain amount of water to your petrol, the ethanol would then be absorbed by the water.

this ethanol + water mixture would then separate from the petrol and sink to the bottom of your container and then you syphoned off the now ethanol-free petrol .

sounded a good idea , but never met anyone who tried it.

if it works the only problem I can see is that you are still left with all the other modern additives still in your petrol and these may also attack glass fibre

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7 hours ago, djr said:

Has anybody tried  removing the ethanol from the petrol before use, as an alternative to sealants etc  ? 

there was at least one company selling a kit     { Ethanil.co.uk , I think was one ? }

I remember reading an article where you added a certain amount of water to your petrol, the ethanol would then be absorbed by the water.

this ethanol + water mixture would then separate from the petrol and sink to the bottom of your container and then you syphoned off the now ethanol-free petrol .

sounded a good idea , but never met anyone who tried it.

if it works the only problem I can see is that you are still left with all the other modern additives still in your petrol and these may also attack glass fibre

Your octane will drop if you remove the alcohol from your fuel,plus the petrol that remains will likely have water absorbed into it. This water will compete with your oil for adhesion to the metal in your engine.

https://www.epa.gov/sites/production/files/2015-09/documents/waterphs.pdf

 

I think I would search out a ethanol free fuel and keep the tank drained when not in use. 

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Anyone having alcohol problems can use alkylate petrol.

Like Aspen which is a quality product.

I use it but mix it with ~1% E85

https://aspenfuel.co.uk/

Several other brands are available.

Edited by carl ekblom

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12 minutes ago, carl ekblom said:

Anyone having alcohol problems can use alkylate petrol.

Like Aspen which is a quality product.

I use it but mix it with ~1% E85

https://aspenfuel.co.uk/

Several other brands are available.

why do you mix it with E85?

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I have read this with interest as this topic is always something worth understanding.  Surely the best way forward with classic tanks would be to build a metal tank then use fibreglass to get the final shape in order to accurately reproduce the original look of the bike?  Modern fuel tanks are plastic and seem to be able to cope with modern fuels.  Old bikes had metal tanks and there was only a short while when other materials were experimented with.

The faff and expense of ethanol free fuels like Aspen is surely greater than the cost of fabricating a new tank from metal then coating it?

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On 9/12/2019 at 10:42 PM, oldtrialer said:

You don't realize how much abuse the side of a tank can get from your knees. It can develop unseen cracks, then eventually leak. My 348 had that problem.

Yes I do realise the pounding the sides of most fuel tanks get especially trials bikes. Pushed and twisted by the riders legs from balancing, turning and the bike dropping to the ground. Lets not forget the errant tie down or rope being tightened down on the tank too! Mud and grit and the seams on riding gear are not a good combination for fuel tanks either. My 250 Sprite tank had a split in the side before I even got it to a trial or practice area. I was just 16 though and impetuous 😳👍 

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