Petrol Tank Sealant

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JimFitz
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Joined: Thu Feb 27, 2014 9:27 am
Location: Kent, England

Re: Petrol Tank Sealant

Post by JimFitz »

I would think that you need some space for expansion when the temperature warms up in the spring. If you have a perfect seal on the cap then something has got to give.
Water is absorbed through the surface of the fuel so filling the tank will reduce the surface area and therefore the amount of absorbed water but as the fuel warms it will escape through the cap breather and dribble down the tank, possibly damaging the paint.

Jim
Too old to Rock and Roll but too young to die.

1952 G80 rigid, 1960 G12 DL / Watsonian Monza, 1954 G80S.
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Expat
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Location: Tennessee, USA

Re: Petrol Tank Sealant

Post by Expat »

Fit a balloon, (or something similar ????) over the open tank filler hole.

:D

Steve
Keep shiny side up.

These are my principles, if you don’t like them, I have others. (Groucho Marx)
Stan Palmer
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Joined: Tue May 27, 2008 2:19 pm
Location: SURREY UK

Re: Petrol Tank Sealant

Post by Stan Palmer »

Preparation of the tank (two in my case) is quite problematic. I followed the POR 15 instructions, first with the Cleaner/Degreaser followed by the Metal prep (acid). Didn't like the result so I bought more chemicals and repeated the process, doubling the standing time recommended for each positioning. Still not that pleased with the result, but its been over a week in process now, and over £100 in chemicals. So I am proceeding with the lining once I have deemed the tanks fully dry. If I need to do another I will certainly seek out a more powerful acid. I am not sure the POR instructions are valid for 70 year old tanks left standing for thirty odd years. I am almost sure that for the AJS tank (done 10 years ago) I used brick acid (relatively cheap) and the inside was much cleaner.

A word of warning: if you use a push in rubber bung at the filler (as I did) be very careful when doing the hot water flush. The first time, I shook the tank, the bung shot out as the air expanded and whizzed all around the room.Lucky not much water with it, but quite a shock for all present (me the dog and the budgie). If you do use that method either don't do it in the kitchen or put the budgie in another room first.
Stan
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GrimJim
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Joined: Thu Jun 21, 2007 11:49 am
Location: KENT UK

Re: Petrol Tank Sealant

Post by GrimJim »

I drain my fuel into the plastic containers used for mower fuel. They do not have a vent,
so the fuel seems to keep well. It's also handy for the mower.

Regards
Jim
MalcW
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Location: DEVON UK

Re: Petrol Tank Sealant

Post by MalcW »

Hi Jim

That's a good idea. Is your fuel tank (or tanks) lined, or do you put something else in them to prevent rusting?

Malc
Mick D
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Location: Aberdeenshire

Re: Petrol Tank Sealant

Post by Mick D »

Hi Malc

Where do you store your bike? do you suffer from rampant corrosion on other items in the same location?

According to the information available acetic acid formation is only an issue on bulk fuel storage tanks, providing that the bike is used it should not be a problem, any minor formation being passed through the engine.

If the bike is going to be stored for the winter months, (about two in Devon as I recall ;) ), I'd use / drain the current fuel from the tank and re-fill completely with new, put the cap on and forget. With full fuel the amount the tank will 'breath' due to temperature fluctuations will be minimised to almost zero.

An empty tank will exhibit the maximum breathing, however as the mass of the tank is not significant it will warm up almost as quickly as it's surroundings and any moist air within will not have time to condense. If you decide to go down the empty route I'd leave the filler cap off, cover loosely with a rag or tissue to keep out dust / insects.

Either way I don't think you'll be bothered with corrosion issues.

I have just restored two bikes which have been laid up with empty tanks in unheated garages for around 40 and 30 years respectively - neither had any more than a thin film of surface corrosion which could be removed almost with a finger.

Regards Mick
MalcW
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Location: DEVON UK

Re: Petrol Tank Sealant

Post by MalcW »

Hi Mick

The bike is stored in an unheated (sometimes it feels colder in there than outside!) garage. It had a lot of muck in the tank when I got it, largely due to the remains of someone's attempt to line the tank. It was cleaned out as well as possible, and a pair of fuel taps with filters were fitted (it only had one at the time, with no filter). I have to say I haven't had any significant corrosion issues since, but I'm keen to minimise any that might occur. I think I'll probably go down the 'fill the tank to to the brim' route during the 2 months (I wish) of winter. And the bike is ready to go, should a weather window of opportunity to go for a ride occurs during that time.

Cheers,

Malc
LynP
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Re: Petrol Tank Sealant

Post by LynP »

My solution to the tank rusting on my 1990; (I know its not AMC but the reason for my post is the metal is much thinner on the FJ) came about because the original tank rusted through in two different places when getting the bike out of the garage in spring two years running and cost me a new tank, at least I could get a new one then! So now every time I lay the bike up I drain the tank and put some two stroke oil in, shake it around to spread the oil and leave it in. The easy part then is to use a small amount of petrol in the spring to wash it out, even if a small amount of oil is left it provided some lubrication on first start up. This new tank has lasted a lot longer so far. If any condensation does form the oil protects the tank especially the base of it Something I have not done but always intend to is to put a small amount of two stroke in the last of the petrol on my last run of the year and that should help the carb also.

Hope this method is of use to others, LynP
numbersix
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Joined: Tue Apr 17, 2018 6:45 pm
Location: North Yorkshire

Re: Petrol Tank Sealant

Post by numbersix »

When I cleaned my G11 tank for sealing, I put caustic soda solution in and let it stand for a day. I then rinsed it out with lots of cold water.

This got rid of the sludge and gunge that had built up in the tank which had been unused for a long time.

I then put a 50/50 solution of phosphoric acid in the tank and left it for a day. This was rinsed out with lots of water and then I dried the tank by blowing a hot air gun in through the filler neck.

The acid removed every trace of rust and also left an ideal coarse surface for the sealant to adhere to.

IMHO, the cleaning chemicals sold by the providers of tank sealants can be hugely overpriced. If the tank is going to be painted anyway (so any spillage on the surface is not a problem,) then caustic soda followed by phosphoric acid (after thorough rinsing) is cheap and effective.

(All of this done at your own risk! Please wear protective gloves, glasses, overalls etc, particularly with caustic soda. Phosphoric acid is relatively safe; it is certainly far safer than muriatic acid at the same concentration. Brick acid is muriatic acid, aka hydrochloric acid. Lots of us will remember the properties of hydrochloric acid from our school days. On the other hand, phosphoric acid is used in Coca Cola........)
Allan.
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