Forks hitting tank

[Guest ratchethack]

Alcohol blended fuels were certainly available in most areas way before the 1999 V11 Sport was made, even before it was designed, even before it was prototyped. Clearly they would not have been issued Euro safety clearance or US DOT status if not using specific "materials".. . .

Clearly, by the time it was fully understood in all situations that many kinds of ethanol-additive fuels caused problems with automotive fuel systems, few adequate long-term materials tests were available. As I recall, it took hundreds of recalls and design changes over a period of about a decade or so before those problems got worked out of the auto industry to a significant degree. In the relatively slip-shodden, hard-scrabble, and outright flaky moto aftermarket industry, it would seem that standards weren't exactly applied the same -- nor to the same schedule.

I'm saying that if, using your chain of thought, the volatile fuel in the tank has compromized the tank material to an extent that it's causing it to expand, clearly it will also leach through the tank material very quickly in it's life, compromising the paint bond 'chemically' rather than 'physically'.

Not a valid assumption, Steve. Just because long-term contact with a certain chemical causes minor expansion of that material is no indicator that the chemical in question will necessarily leach through pervaseively enough to cause paint bonding problems, chemical or physical (the difference being what, I don't know??) -- let alone "very quickly".

 

In a similar, but non-fuel-related scenario, early fiberglass hull boats suffered osmotic blistering of the gel coat only after many years in the water -- some didn't have any identifiable problems until they'd been in the water continuously for over a decade. IIRC, there weren't ANY paint bonding problems of any kind -- and that was on the same side of the gel coat as the water. Once the osmotic pressure problem had been identified, new formulations of resin were developed that eliminated the problem.

 

And so it was for many automotive industries before they discovered what kinds of o-ring, gasket and seal compound formulations withstood long-term effects of ethanol in fuel. How many different plastic formulations d'you figure Ascerbis has used in their plastic gas tanks over the years? D'you reckon wot they're using today is the same exact formulation they used 10 years ago? 10 years before that? I had an aftermarket Ascerbis tank on my '69 Bultaco Pursang. D'you reckon they still use the same plastic formulation today? Setting that aside, d'you reckon the standards testing for moto fuel tanks have changed any between the advent of ethanol-additive fuels and today?

 

Look, I'm not interested in arguing with you on this. Temperature expansion aside, my fuel tank has most definitely got larger by a tiny fraction of a percentage, and many others have observed the same -- it's not anyone's imagination.

[Steve G.]

Clearly, by the time it was fully understood in all situations that many kinds of ethanol-additive fuels caused problems with automotive fuel systems, few adequate long-term materials tests were available. As I recall, it took hundreds of recalls and design changes over a period of about a decade or so before those problems got worked out of the auto industry to a significant degree. In the relatively slip-shodden, hard-scrabble, and outright flaky moto aftermarket industry, it would seem that standards weren't exactly applied the same -- nor to the same schedule.

 

Not a valid assumption, Steve. Just because long-term contact with a certain chemical causes minor expansion of that material is no indicator that the chemical in question leaches through pervaseively enough to cause paint bonding problems, chemical or physical (the difference being what, I don't know??) -- let alone "very quickly".

 

In a similar, but non-fuel-related scenario, early fiberglass hull boats suffered osmotic blistering of the gel coat only after many years in the water -- some didn't have any identifiable problems until they'd been in the water continuously for over a decade. IIRC, there weren't ANY paint bonding problems of any kind -- and that was on the same side of the gel coat as the water. Once the osmotic pressure problem had been identified, new formulations of resin were developed that eliminated the problem.

 

And so it was for many automotive industries before they discovered what kinds of o-ring, gasket and seal compound formulations withstood long-term effects of ethanol in fuel. How many different plastic formulations d'you figure Ascerbis has used in their plastic gas tanks over the years? D'you reckon wot they're using today is the same exact formulation they used 10 years ago? 10 years before that? I had an aftermarket Ascerbis tank on my '69 Bultaco Pursang. D'you reckon they still use the same plastic formulation today? Setting that aside, d'you reckon the standards testing for moto fuel tanks have changed any between the advent of ethanol-additive fuels and today?

 

Look, I'm not interested in arguing with you on this. Temperature expansion aside, my fuel tank has most definitely got larger by a tiny fraction of a percentage, and many others have observed the same -- it's not anyone's imagination.

 

Well, don't worry Ratchet, I'm not about to get into a conversation with you on this one. I've seen what can happen when a contrary view is offered, the insanity of the global warming thread comes to mind. Unlike yourself, I'm not a chemical engineer, so when you say my assumtions are incorrect in every aspect here, I'm just going to shrug my shoulders and move on, it's not worth the sore typing finger. Obviously your background in plastic technology surpasses mine as well, so I'll call you next time I need advice on that as well.

Good luck with your swelling tank.

Steve

[Greg Field]

When nothing else can swell, you latch onto your tank . . . er so enquiring minds . . . swell . . .

[John in Leeds]

When nothing else can swell, you latch onto your tank . . . er so enquiring minds . . . swell . . .

 

So how much more fuel do these 'swelling' tanks contain? Do they fetch a premium from the Iron Butt crowd? How long will I have to wait until my tank has significantly increased in value?

 

Expanding minds ........

[scre103]

the fork hit my tank on the left side of my 2001 v11 due to the swelling tank phenomena that many v11 owners experienced back in the day when there was about 12 feet or so of rubber hoses and california emission vapor absorbtion cannisters stuffed under the seat. Some blaimed a faulty fuel line check valve under the tank, and they poked holes/removed/replaced them hoping it would help. Others drilled holes through their gas caps. there were all kinds of things people were doing to their bikes to get rid of the so called " tank suck" condition that these early v11's suffered from. if you go back far enough in the forum post history, you will find dozens of posts on this topic. i had all the emission stuff removed and placed caps available from bmw on the zerks where the black hoses come off on both sides of the throttle bodies. this greatly reduced the shrinking and expanding of the tank. this seemed to be the most popular fix. there are still some minor expansion changes like ratchethack pointed out.

[Guest ratchethack]

Anybody reading this try elongating the rear mounting hole of the tank to allow it to sit farther back on its front mounts?

 

In my case, it looks like this would be a safe way to stop tank interference with the fork stanchions. I'd also have to relieve the 2 contact points at the back of the tank at the forward mounting lugs of the rear carapace by shaving the lugs down. One side is now in full contact (forcing the tank forward on its flexible forward mounts), the other side has ~1 mm of clearance. When I took delivery of the bike, as I recall, there was at least 6-7 mm of clearance at these points with the tank fully snugged-up. Having shimmed up the rear of the tank vertically for side-cover clearance seems to have accounted for less than 1 mm. of loss of horizontal clearance, since the rear of the tank is slanted.

 

NOTE: By my measure, the expansion of the tank has been just under 1%.

 

EDIT: On closer inspection, the tank has apparently been pushing back against one lug on the rear carapace for some time. There's a 10x5 mm area worn through the paint and a into the plastic on both the tank and the lug on the left side. I'll be relieving both lugs considerably for clearance next time the tank is off.

[Greg Field]

Is it swelling outward toward the sides as well as in length?

[Ray]

FYI,

 

Mine has been contacting the forks since about 04. I don't see it as the tank swelling but the two forward tabs of the tank on either side of the headstock distorting outward from age, heat, and and tank sucking. I have aluminum debris rubbed onto the tank and some grinding of the plastic underneath on the mount where it meets the bumper on the frame up front. I assume with time it will rub through and will start leaking. Bike has about 25,000 miles.