quick question - 74 Mk2 fuel tank - sealant, factory or otherwise...

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joe czech

joe czech

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finally got around to dumping the 6 year old gas from the tank. when I bought the bike, it only had about 1 gallon of gas and the upper-inside of the tank appeared to be rusty. long story short, dumped the gas, and what I thought was rust turns out to be some sort of textured, tan sealant or coating. the dumped gas seemed to be clean and clear, and didn't show any signs of suspended rust particulate mixed in with the gas, so i'm thinking i'm good to go. after the tank dried out, it appears to have been sealed, so the question - are these things sealed from the factory or is this something a previous owner applied? should I have any concerns? still pretty new to this. thanks....
 
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No seal applied at the factory. The age of the lining is critical, pre alcohol type and it will dissolve in the E5+ fuel and then deposit itself in the carb blocking jets and into the engine sticking valves in guides etc. If its designed for post adding of alcohol then you have a better chance, depends on the types, some work some do not.
 
kommando said:
No seal applied at the factory. The age of the lining is critical, pre alcohol type and it will dissolve in the E5+ fuel and then deposit itself in the carb blocking jets and into the engine sticking valves in guides etc. If its designed for post adding of alcohol then you have a better chance, depends on the types, some work some do not.
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OK, so no factory sealant. the age of the lining or sealant is unknown - i'm assuming pre-2006. unknown type of residual gas in the tank, that is, don't know if it was ethanol or non-ethanol. what ever it was, the lining or sealant doesn't seem to be affected by gas. I do know the last time the bike ran was in 2013. when I get it running, most likely, i'll be using 89 octane non-ethanol - readily available and local.
 
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Suggest you remove the carb float bowl and p/tap and look at both filters and bottom of the bowl. Any deposits on there will give you an indicator of whether the “lining is breaking up or not.
 
Bernhard said:
Suggest you remove the carb float bowl and p/tap and look at both filters and bottom of the bowl. Any deposits on there will give you an indicator of whether the “lining is breaking up or not.
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good point. no filters on the (aftermarket) petcocks. the bike came with a single mikuni - that was installed sometime between 2006-2013. I tore down the original amals, and the internal filters appeared to be clean. I'll open the mikuni and check the internals.

edit - there was in-line fuel filters with the aftermarket fuel lines - will also check those.
 
With so many problems associated with ethanol mix in the fuel I used a rust remover “Metal Rescue” on a steel tank I’m working on. The tank came out very clean. I will not use any liner as there was nothing I tried that could safe the fiberglass tank.
 
Getting the lining out of the tank is not a straight forward project. I bought a tank a number of years ago that had a tan liner in it and I finally got it to break down after letting the tank sit full of offensive solvents for a long period of time. Which of course made me wonder why I was trying to get it out but once it started coming loose there was no turning back. Eventually the tank was placed inside a cement mixer. I wrapped it in packing blankets so that it didn't get battered and filled it with solvent and drywall screws. Then let it spin for days. Of course it was necessary to seal the openings and no I didn't manage to do this without screwing up the paint. Sadly I don't remember now exactly which solvent worked best. I know I tried MEK, acetone, xylene. Not in combination. My impression at the time was that none of them worked very well. It was a long process.

I don't know if anybody has found a simple way to remove lining from a tank.
 
POR-15 is a three step process for lining tanks. Step one and two are claimed to strip out any previous liner
 
If paint wasn't a concern I wonder if the bad liner could be burnt out using a propane torch on a properly De-gassed tank? Liners are typically some kind of urethane or epoxy which are combustible. Pretty nasty smoke will no doubt need proper safe venting.
 
While forgetting about trying to preserve the outside paint job, immerse the inside with aggressive paint remover. Continually
revolve the tank for a couple of days. Once the liner is "loosened" and all is rinsed out, successive soakings with acetone and or MEK
will eventually remove all of the liner. Not a fun project and quite toxic.
While I have (successfully?) lined a couple of tanks with Caswell's tank sealant, I will never again line a tank. It's just a mess when/if
it has to be removed.
 
johnm said:
POR-15 is a three step process for lining tanks. Step one and two are claimed to strip out any previous liner
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That's interesting and probably worth trying. Whether you use their sealer or not. According to their web site:

Kit Contains
  • POR-15 Strip to remove competitors failed sealer
  • POR-15 Cleaner Degreaser to remove gum, sludge, varnish
  • POR-15 Metal Prep to remove rust & prepare tank for sealer
  • POR-15 Fuel Tank Sealer creates a permanently sealed tank
  • POR-15 Power Mesh for sealing large holes or reinforcing weak areas
  • Applicator for applying patching system to exterior of tank
  • Detailed Instructions to take you easily through each step of tank restoration

I've used a number of POR-15 products in various applications. They make some good products. I suppose one of these days, somebody will develop something that actually works for lining a tank. I'm such a cynic now that I doubt I'll be the guy that discovers it.
 
Esmerela said:
Hi Joe

I have only seen the brown goo sealer in the tanks from India.
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99.999999% sure it's the original tank, original paint, etc.. last pic is the tan sealer - not pretty, but i'm guessing it works - ???????

curious about the POR-15 system - may research it a bit, but not sure what path to take at this point. as I said in my original post, when I dumped the 6 year old gas, the was nothing suspended in it, so whatever type of sealer I have, it seems to be holding up.

quick question - 74 Mk2 fuel tank - sealant, factory or otherwise...


quick question - 74 Mk2 fuel tank - sealant, factory or otherwise...


quick question - 74 Mk2 fuel tank - sealant, factory or otherwise...
 
That is a nice paint job. If you do go with any kind of chemical stripper for the sealer then you will have to be very careful to protect it.

I spent ages taping and protecting my paint before doing the tank cleaning step. I was only dealing with rust and not a failed liner
 
Looking at that tank and the fact the old gas came out clean, plus the fact you plan to use non ethanol gas I would just try it. Maybe put an inline filter in the gas line and keep a close eye on it.

I think I’d just try it and monitor results

and maybe not set out on a 1000 km trip in the first week ;-)
 
johnm said:
That is a nice paint job.
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well. it looks nice from an arms length. if you get up close, the 45 year old lacquer does show it's age. right now, I don't have the heart to put an end to it for a full repaint. I know the world only needs so many museum pieces, and this isn't one of them, but you can still see a lot of history in the old girl. she's been neglected, abused, and somewhat ignored for too many years - i'll be happy just to get her running - ;)
 
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I agree you might be in good shape.

I don't recognize the white numbering?

Question: Can an original tank be identified by the welding technique of the baffles vs. that of a reproduction. Here I am just looking into the tank through the cap hole and comparing the spot welds.
 
Jdub said:
I agree you might be in good shape.

I don't recognize the white numbering?

Question: Can an original tank be identified by the welding technique of the baffles vs. that of a reproduction. Here I am just looking into the tank through the cap hole and comparing the spot welds.
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as to the white numbering - there was a thread a short while ago, and the lettering or stamping topic came up ( https://www.accessnorton.com/NortonCommando/fuel-tank-mounts.28729/). at the time, no one could identify or decode it. in the thread, member "marshg241" had a pic of an original tank and he could somewhat make out a faint marking (C8 17 R - ???). at first I thought it was some sort of julian date code, but it's beyond the august 74 build date of my Mk2. best I can determine, and JUST GUESSING, but i'm reading the "R 269D" as "R" for roadster, "269" maybe the 269th tank built, and "D" - unknown - maybe "D" the fourth letter, as in 197"4". one thing certain, and fairly obvious, the stamping was after the painting process, and there's a meaning for it. i'm really confident my tank is original to the build - no reason to suspect otherwise. any owners with original tanks and paint have similar markings?

as far as the internal baffles and welding - I don't have near the experience to comment on that.

:)
 
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