WTF Is This? - Set Screw in Gas Tank and Tank Sealer

murphus

murphus

Senior member
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Lost in the Midwest
This has me somewhat baffled. Slowly putting the 1984 "Colorado RGS" back to running order. Reinstalling removed bodywork. First pic shows right side of tank where fairing extension secures with two allen head bolts. I didn't notice anything odd taking it apart, but going back together noticed the upper threaded fixing point appeared to be but maybe 3mm deep, with only a few threads showing. Further examination showed an allen head set screw firmly screwed home. WTF?
Second pic shows the inside of the gas tank. Curious as to the tank's internal condition, I removed the sending unit. Previous owner lined the tank, and from what I can see for no reason. Metal is all super clean. Looks to be an epoxy-type liner. It's yellowed, hard, but cracking and starting to separate from the steel. I'm inclined to run it as is, avoiding alcohol-blended fuel. I don't see anyway one could remove it without cutting the underside of the tank out ...
I considered the idea the set screw was inserted to seal a hole in the tank maybe caused by someone using the wrong length fixing screw for the fairing and somehow punching through the tank, with the liner installed to further seal the tank, but there's no indication of any damage at that point.
 

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It,s unfortunate the tank sealer is breaking apart and you can only remove the loose chunks and keep an eye on it. Not sure if there,s a solvent or method of safely removing it without damaging the tank.
 
TeddyG said:
Not sure if there,s a solvent or method of safely removing it without damaging the tank.
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Acetone will dissolve epoxy resin, It'll need to soak for a while (possibly up to a few days) but it'll eventually dissolve. There are other chemicals that'll do the job too, such as MEK, methylene chloride or toluene, but they're quite toxic. Acetone is probably the easiest and cheapest to get hold of, and not quite as horrible as the other stuff.
 
Do not use resin in tanks.
Paul

Funny that my carbon fibre tank is held together with epoxy resin, and 10 years of containing fuel there is no sign of leaks.
 
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Reactions: Rob
Dellortoman said:
Acetone will dissolve epoxy resin, It'll need to soak for a while (possibly up to a few days) but it'll eventually dissolve. There are other chemicals that'll do the job too, such as MEK, methylene chloride or toluene, but they're quite toxic. Acetone is probably the easiest and cheapest to get hold of, and not quite as horrible as the other stuff.
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My biggest worries would be protecting the paint and ensuring the slurry of acetone/resin is fully removed, although maybe with the fuel sender removed and the benefit of the filler neck it wouldn't be that bad ...
 
motoddrob said:
Do not use resin in tanks.
Paul

Funny that my carbon fibre tank is held together with epoxy resin, and 10 years of containing fuel there is no sign of leaks.
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Good point Rob. Maybe being actually MADE of epoxy resin there isn't the problem of separation (metal from epoxy), which seems to be what happens when it goes pear-shaped.
 
motoddrob said:
Can't blame the product, it all comes down to prep. I'm not a fan of liners but if I were to use a liner it'd be Caswells epoxy.
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I've used Caswells in my RGS, seems to be holding well.
Word of caution, the standard Caswell kit is suitable for a regular tank, BUT the RGS tank has a much larger surface area and requires 2 kits to fully cover the internal surface.
 
I have used slosh, got me out of trouble and lasted 2 years, then the trouble began, changed tanks and cut the bottom out of the old one, metal grit blasted both top and bottom to remove resin, rust, filler, etc and woh! it was tinworm at its finest, minor pin holes that can only be seen when you hold thetank up to bright sunlight, or placed in front of a 750watt Halogen lamp, and lots of realy big ones that you can put 2, 3 or even four fingers in, almost a whole new tank bottom required.
CLEM
 
Did exactly the same with a Triumph tank once, only it was carby-blocking rust. The fix, the Creme crap was worse than the rust in the end. The Castwell stuff, they came out with a 3 stage treatment that included way better tank cleaning back then. I have heard is the best of a bad lot but if you do it follow their instructions by the letter and go to extremes with the prep or you will end up regreating it and going the full weld route anyway. The only prep anyone used back then was diluted strong acid, in the tank for as long as required, nobody had heard of Epaporrust citric acid or Eletrolisus back then in the late 80s. That Creme shit just made it harder to do a good fix.
 
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