Unexplained Phenomena

My fiberglass tank on my '71 Commando got a dose of E10 gas before I was aware of the consequences. Sure enough, the area at the bottom of the tank where the sides joined it showed signs of the swelling and the outline of the seam. That was at least 10 yrs. ago and I went ahead and tore it down for a rebuild. That's been dormant for awhile, but I'm making it a priority to bring it back to life again. Well, I started organizing the various components this week.
Lo and behold, the tank now shows no signs of the E10 damage. That's pretty amazing that the swelling relaxed and the fiberglass resumed it's original dimensions. Of course, Casewell will be on the job now!

What does it meant to tear a gas tank down for a rebuild?

I tore the entire bike down for rebuild.

There is an interesting thread on this website about a fellow (Jean??) who did tear a fiberglass tank down for a rebuild. Lots of work, but one solution to the problem.

Yes, I did read that. Maybe worth the effort for a fastback tank, but for roadsters, I'd just go over to steel. I will utilize an OEM steel tank for the build, but I just found it really interesting that the fiberglass shrank back to it's original shape after several years.

Deckard said:

Yes, I did read that. Maybe worth the effort for a fastback tank, but for roadsters, I'd just go over to steel. I will utilize an OEM steel tank for the build, but I just found it really interesting that the fiberglass shrank back to it's original shape after several years.

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Shrinkage to original size is well enough known. On poulan and pioneer chainsaws (+others?) the fuel cap swells up from the E-10. Almost can't get them out except with big channel locks.
Drain the tank and put the cap on the shelf for a few weeks and it shrinks down to original size and screws back in just fine.
I now never use e-10 for 2 stroke mix.
Ethanol dissolves the polyester resin and then the engine eats it and sometimes blows up.

Many years ago I made a polyester/glass tank and put methanol in it. The methanol went through the bottom of the tank and ran all over the motor at a race meeting. So I then bought two-pack epoxy and coated the inside of the tank with it. The tank still leaked. I think that if you are going to do that, you must remove every last trace of oil before you apply the epoxy. - several rinses with acetone ?

From all the horror stories I read on this and other motorcyle forums, I concluded that it is not worth to put time, effort and money in attempts to save polyester tanks from the destructive effects of ethanol fuel.

Unless you have a confirmed ,lasting source of real gas ( non- ethanol) ... then there is no reason to turf your original tank until you break it ...

Why rehash the same old topic over and over again?
Suggest doing a search: fiberglass member: dynodave
23 results with 6 or so going in extreme detail.
Yes my featherbed (fiberglass) dunstall tank project has stalled, but is not forgotten.

acotrel said:

Many years ago I made a polyester/glass tank and put methanol in it. The methanol went through the bottom of the tank and ran all over the motor at a race meeting. So I then bought two-pack epoxy and coated the inside of the tank with it. The tank still leaked. I think that if you are going to do that, you must remove every last trace of oil before you apply the epoxy. - several rinses with acetone ?

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No glue will stick to an oily surface, in fact it would be better to “rough-up” the surface provide a “key” before applying any epoxy.

Out of curiosity I tried the search as suggested - fiberglass + dynodave - but only got 9 results, none of which were Dynodaves. Obviously I did something wrong search-wise but not sure what.


Lacquer thinner in the tank to wash it out followed by a couple handfuls of small sheet rock screws, shaken, not stirred for several minutes and it will be ready for Caswells.

I wouldn't argue against replacing an FG tank with steel but:

1. I am not aware of any steel fastback tanks

2. As I posted in a related thread, my Caswell coated FG Fastback tank has been totally unaffected by fuel in any way for over 10 years now.

Bernhard said:

No glue will stick to an oily surface, in fact it would be better to “rough-up” the surface provide a “key” before applying any epoxy.

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Having worked with fiberglass starting in 1980...
Actually when polyester resin fabrications are done, the final coat is very commonly added with paraffin (wax not kerosene). The paraffin is expelled and floated to the surface as part of the chemical reaction. The final wax coat is the "inside" surface of the tank. The wax solidifies and coats the resin to exclude air/oxygen contact that would otherwise inhibit surface hardening.
This paraffin is never cleaned off and is not gasoline/acetone/what ever??? soluble. Not a problem for only gasoline in a norton tank.
My theory is:
Now 40 years later you try and coat the tank with novalac epoxy and guess what??? It does not stick worth a damn/fisheye???, and it does not adhesion coat real well. The result is tiny porosity in the novalac that allows E-10 to get through to the polyester resin.
Also I can not conceive that caswell that uses novalac epoxy that is E-10/ethanol resistant, not proof, to be a final cure when only surface cleaning above and beyond a casual slosh of a cocktail of chemicals against the highly resistant wax.
I alway felt if the tank was cut open and a real surface prep was done you might have some hope of preventing polyester leaching into the E-10. "Rough up" may not fully remove the residual wax, only smear it around.

MM
no such forum member as "Dynodave"
search: fiberglass
next line
Member: dynodave
now 25 thread results

Well, that's interesting, I was just following the info in Post 10, copying the suggested search string, fiberglass + dynodave, and entering it to the search window. So I'm confused!

Interesting where this is going. Yes, as Dave says, sealing a fiberglass tank has been well documented. I just thought that the exterior E10 damage disappearing after about 13 years was an interesting observation worth noting. After seeing the damage for so many years while it was on the shelf, it was a nice surprise to see the warpage gone...

Back to the original subject, has anyone ever noticed that when you personally ingest alcohol that your body also seems to swell? What's up with that? Must be some kind of black magic. Wine seems to make my waistline increase at the fastest rate. Then, just as Deckard observed, if you take away the alcohol things shrink back down to their original dimensions. So weird!

Don't understand, after ingesting alcohol, you notice a change? You are not ingesting enough, or are using the wrong type.
To achieve stability, steady consumption is required, then no increase in size occurs or if it does, continued consumption prevents detection. This approach (with help from Ebay) caused my leaking Fi-Glass Roadster tank to morph into a steel Roadster tank so all good IMHO. Not weird at all.
Cheers, Martin (time for another I think)

eskasteve said:

Back to the original subject, has anyone ever noticed that when you personally ingest alcohol that your body also seems to swell? What's up with that? Must be some kind of black magic. Wine seems to make my waistline increase at the fastest rate. Then, just as Deckard observed, if you take away the alcohol things shrink back down to their original dimensions. So weird!

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Ah yes, as Dirty Harry once said "A man's got to know his limits" As I say "How do you know your limits until you exceed them?"