900 Super Sport Carbon Fiber Gas Tank Leaking

Jeff Higgins · 09-30-2021, 10:28 AM

...again. *Sigh*. Been a problem ever since ethanol gas has been all that is available, at least conveniently. The main laminates have been just fine, with the resin used on them holding up quite well. The problem is, it's necessarily a two piece design. It's a large "tortious shell" upper with the bottom glued into it with some other sort of glue or resin. That's the part that has failed.

I separated the halves years ago the first time this started and reattached them to one another with a two part epoxy billed as "gasoline proof". Well, maybe it is, if it isn't left to soak in it for, well, maybe a decade or so. I'm not sure anything will stand up to that.

One option, of course, is to drain the tank when it's just sitting in the garage, thereby limiting exposure. Kind of a PIA, but it does have an electric fuel pump, somewhat lessening that burden. Maybe over the winter...

So, I now have it "repaired" and back together again. Now I'm thinking of trying a different approach, and have ordered some gas tank sealant from Caswell. They advertise it as carbon fiber and fiberglass tank specific. I was kind of reluctant to go there, since I've heard horror stories about products like Kreme coming off in steel tanks and really causing problems. So, wish me luck. I'll keep you posted.

Zeke · 09-30-2021, 10:30 AM

If anyone can figure this out, it's you.

flipper35 · flipper35's Garage

Some home built planes use composite tanks, what do they seal with?

id10t · 09-30-2021, 10:39 AM

Any way to put a bladder or liner inside the tank?

Jeff Higgins · 09-30-2021, 11:30 AM

Thanks, Zeke, I wish I had that kind of confidence in myself.

Many homebuilt planes, along with a broad variety of boats, use some form of plastic or compost gas tanks. When I first researched this issue about ten years ago, there was a lot being said about the problems they were having with ethanol based fuels. It became my understanding that, due to these problems, marinas and airports (for the most part at least) quit carrying the stuff. Imagine having the seam on a composite tank, that has been laminated into a fiberglass boat hull, begin to leak. I guess there were some fires, lawsuits, and all of that. I never heard of any failures in aviation, but they have their own issues with ethanol, its vapor pressure leading to problems at altitude, etc. So, i the end, both disciplines solved their problems by eliminating ethanol based fuels. I wish I could do that, but as much as I ride the darn thing, it just wouldn't be convenient. Coming up on 95,000 miles on it, believe it or not.

I had thought of putting some kind of a bladder in it. The logistics of that would be pretty daunting. I wonder if anyone has ever done this on a motorcycle.

Zeke · 12:31 PM

I looked and someone has taken out a patent for a thermoset tank bladder. I guess they blow it up like a balloon inside a vessel and then bake it. I suppose hot air could be used on larger tanks that can't be placed in an oven.

Think of the possibilities if that came to fruition.

rfuerst911sc · 09-30-2021, 12:58 PM

Are there aftermarket metal tanks available ?

javadog · 09-30-2021, 01:13 PM

Yes, aluminum tanks are the way to go. There’s an entire cottage industry in the UK making these things, many are fairly reasonably priced. You can also get one made in Japan, here’s the company I would use for that:

https://beater-japan.com/?p=126

Yorkie · Yorkie's Garage

Guzzitech on ebay has a decent SS steel tank for sale. At $650 it's not cheap but the last time I spoke to him he mentioned that SS parts are drying up.

https://www.ebay.com/itm/274684910426?hash=item3ff47f1b5a:g:eVQAAOSwJTNgKri A

Chocaholic · 09-30-2021, 02:06 PM

Jeff…I drive 20 miles every few weeks to fill four 5 gallon gas jugs with 90 octane ethanol free gas. I put a shot of Seafoam in them and use them to fill my bikes in the garage. Occasionally on a longer ride I’ll have to put in 10% ethanol but it’s diluted with real gas.

Seems like less hassle than what you’re dealing with. No idea about your access to real gas but f within a reasonable distance, might be worth considering once you get your tank sealed.

greglepore · 09-30-2021, 02:25 PM

Well the steel ones rust in the bottom corner then pee gas on your leg, so damned if you do...

javadog · 09-30-2021, 02:28 PM

Which is why I prefer aluminum. I’ll probably build two more bikes before I’m done, each will have an aluminum tank.

Rawknees'Turbo · 03:34 PM

Jeff, Caswell (two stage mix) kicks ass. I made many attempts to repair a fairly rusted and leaking fuel tank for a vintage Lincoln arc welder, and nothing worked until I discovered Caswell sealant. I also learned along the way that any single stage sealer is shiit (Kreem, Wurth, POR, etc) as it never completely dries/hardens (simply skins over and stays gooey beneath the skin), so eventually fails.

Jeff Higgins · 09-30-2021, 03:56 PM

Dayum - that aluminum tank is sah-weet! I would polish it up and clear coat it. But, hoo boy - $2,100 is a fair chunk of change.

I've considered picking up a steel tank before they are all gone, just in case. But, like Greg points out, they rust in the bottom rear corners. That part of the tank is actually below the float bowls, which is why they need the internal electric fuel pump. And since it is so low, and drops below the rest of the tank floor, it collects water. And rusts. Repairable, for sure, and maybe I'll grab one just because.

I do like the two part epoxy approach of Caswell. I've heard the same complaints about the single stage products creating a gooey mess that eventually lifts, creating bigger problems than they solve. A two part epoxy should be far more resistant to gasoline and ethanol.

"Supply chain" issues are a big deal to me. Granted, most of my riding is "out and back", so I could keep gas cans in the garage. There is non-ethanol available in my area but, unfortunately, I would burn half a tank just to go out and get it. It would only make sense if I went out in my Land Cruiser with some gas cans and loaded up. I may wind up doing that, and draining the Ducati tank when not in use.

Unless the Caswell lives up to its reputation. That would be ideal. I really want to keep the carbon fiber tank, it's a large part of the "ness" of this particular bike. The other solutions will only be explored if my hand is forced, if the Caswell doesn't seal. It's on its way, and the tank is prepped and airing out.

sc_rufctr · 09-30-2021, 06:04 PM

Quote:

Originally Posted by javadog

Yes, aluminum tanks are the way to go. There’s an entire cottage industry in the UK making these things, many are fairly reasonably priced. You can also get one made in Japan, here’s the company I would use for that:

https://beater-japan.com/?p=126

Nice but why not make your own?

javadog · 09-30-2021, 08:33 PM

Quote:

Originally Posted by sc_rufctr

Nice but why not make your own?

Actually, for one of my projects, and perhaps the other, I do intend to make my own. I will most likely construct them from hydroformed pieces, as opposed to what he does.

sc_rufctr · 09-30-2021, 10:19 PM

Hydroforming is cool. I've seen it done in someone's backyard using a power washer.

Rot 911 · 10-01-2021, 06:43 AM

All of the guys on the Norton motorcycle forum swear by Caswell for lining their old fiberglass gas tanks. Good luck!

unclebilly · unclebilly's Garage

I had tons of fun with large flakes of gas tank sealant coming off in my Unimog fuel tank… the thing would starve for fuel and suck air, usually at the worst timing and worst spot. More than once I was standing in water up to my knees hand pumping the lift pump plunger so it would start again.

Once started it would be fine for 100’ or 100 miles. You never really knew…

I put a chunk of scotchbrite over the intake tube to keep out the flakes and eventually replaced the tank.

Jeff Higgins · 10-01-2021, 02:52 PM

Quote:

Originally Posted by Rot 911

All of the guys on the Norton motorcycle forum swear by Caswell for lining their old fiberglass gas tanks. Good luck!

That is exactly where I first read about Caswell sealants. I figured is anyone knew composite gas tanks, it would be those guys. They do sing Caswell's praises, so I'm optimistic that I will see the same good results they have.

I had to laugh, when in one of their discussions one of them was warning others away from the single stage (Kreme, POR15, etc.) sealants. One of the responses chastised him for having obviously rushed the process, not having given his tank sufficient time for all of the gasoline that soaks into the laminate to have evaporated. His reply was classic British understated "piss off" - he replied by saying "this particular tank had sat unused on the top shelf over my work bench for 37 years. Perhaps I should have given it 38?" Gotta love it.