FG fastback tank...Hmmm

mike996 · Nov 18, 2013

I seem to have sung the praises of "modern" FG tanks a bit prematurely ...

As recently as a week ago I had stated that I had had no issues with my FG tank purchased new from Burton Bike Bits several years ago. But yesterday while out for a ride and with the bike parked in front of the Longhorn bar/grill here in San Miguel de Allende (Mexico), I discovered several small cracks in the top surface of the tank. They are not soft and there is no sign of fuel seepage so I don't know whether they are fuel related. On closer inspection I also noticed that the color (BRG) of the tank is now a bit mottled. So clearly something is going on with the FG.

Not sure what, if anything, I am going to do about it at the moment other than keep an eye on it. I suppose it could just be some sort of surface (gelcoat) cracking. In that case it wouldn't be much of a problem to fix...I've been thinking of changing the bike's color anyway... I kind of like yellow but my friend's CNW Norton is a yellow fastback so we don't need two of them here! Maybe red. My first Commando back in the day was a red roadster...

If the tank is a serious problem, I guess I could revert back to the roadster that it was before I converted it to a FB. Since I have all the roadster parts, I'd probably do that before I'd pay the money for a metal FB tank. But here's hoping it's a gelcoat issue, not a resin issue.

Bob Z. · Nov 18, 2013

What type of fuel are you using?
I think the issue with fiberglass/composite construction is that ethanol fuels would affect the material.
Ethanol has even affected more modern lined and composite fuel tanks.

I believe that a vintage Norton tank can still be reliably used if non-ethanol fuels are used.

Remember that the fiberglass tanks were originally removed/banned because of the safety issue. During a crash the tank could fracture and spill fuel that could cause a devastating fire.
The early tanks used a rubber band to secure the rear of the tank to the frame. In a hard front end bump the tank would tilt up and forward and rip the two front mounts out causing a fuel spill. Metal rear strap is much more secure.

mikegray660 · Nov 18, 2013

mike i'd keep a damn close eye on that - i had a tank go over time (despite caswell coating etc) and the fiberglass that dissolved in the fuel ended up coating the entire intake system, causing a valve to stick w/ the expected catastrophic results - i'll never use a fiberglass tank again despite all the claims of "ethanol" proof etc etc - if your carb slides start to stick its a sign that the tank is going
m

mike996 said:
I seem to have sung the praises of "modern" FG tanks a bit prematurely ...

As recently as a week ago I had stated that I had had no issues with my FG tank purchased new from Burton Bike Bits several years ago. But yesterday while out for a ride and with the bike parked in front of the Longhorn bar/grill here in San Miguel de Allende (Mexico), I discovered several small cracks in the top surface of the tank. They are not soft and there is no sign of fuel seepage so I don't know whether they are fuel related. On closer inspection I also noticed that the color (BRG) of the tank is now a bit mottled. So clearly something is going on with the FG.

Not sure what, if anything, I am going to do about it at the moment other than keep an eye on it. I suppose it could just be some sort of surface (gelcoat) cracking. In that case it wouldn't be much of a problem to fix...I've been thinking of changing the bike's color anyway... I kind of like yellow but my friend's CNW Norton is a yellow fastback so we don't need two of them here! Maybe red. My first Commando back in the day was a red roadster...

If the tank is a serious problem, I guess I could revert back to the roadster that it was before I converted it to a FB. Since I have all the roadster parts, I'd probably do that before I'd pay the money for a metal FB tank. But here's hoping it's a gelcoat issue, not a resin issue.

mike996 · Nov 18, 2013

From what I've been told, the gas here in Mexico does not contain ethanol But I don't know that for sure. There is only one brand - Pemex - so there is no opportunity to try someone else's fuel. My tank is a replica of the original FB tank - cap with hinge on the forward side of the filler and the big O-ring to hold the rear.

Looking closely at the tank cracks with a strong light and magnifying glass a few minutes ago, it APPEARS that it's just gelcoat cracks like boats (and Corvettes) typically get. But, as suggested, I will be keeping a very close watch on this and if any seepage or sticking of slides occurs, I'll restore the bike to it's original steel tank roadster configuration. I love the FB look but I don't want to spend the money for a metal FB tank when I have all the parts to put it back to the Roadster configuration. OTOH I really like the greater range of the FB over the R. The R is a little too short-legged for me while the interstate is the opposite. The FB is "just right!"

Jeandr · Nov 18, 2013

mike996 said:
From what I've been told, the gas here in Mexico does not contain ethanol

I'm sure it's Tequila :mrgreen:

Jean

FG fastback tank...Hmmm

mike996

Bob Z.

mikegray660

mike996

Jeandr

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