Why does a SJ gas tank yellow?

[mbrick]

What causes the nice, new white SJ gas tank to yellow over time? Would like to keep mine white.

It can't be UV exposure, since the hood covers it. Is it gas+oil liquid contact or fuel vapor?

Wondering if I store my tank with a few teaspoons of gas remaining in the bottom will the vapor yellow the whole tank? OR will it only yellow where liquid fuel is in contact over time?

Do I need to siphon it dry and leave the cap off before storing?

I normally store with stabilizer and the tank nearly empty but the res line and carb still full. Would prefer to keep fuel fully in the lines/carb with fuel stabilizer rather than blow out the lines so small amounts of fuel that remain can evaporate and leave crap in small passages.

 

[DAG]

http://www.x-h2o.com/index.php?threads/why-do-gas-tanks-turn-yellow.103294

 

[mbrick]

My search-fu was weak. I didn't try hard enough.

Still no good answers. It's definitely not from UV exposure, and the white stripes under the straps is intriguing.

I guess the plastic may just be degrading over time.

I'll try fully draining it next time I ride.

 

[Pro-pulsion]

I have read this before but not on the X. I believe it has something to do with the chemical properties of the plastic and the oxygen/hydrogen atom exposure. Through time as the tank becomes more abundantly exposed to water and oxygen both atmospherically and bonded to the fuel internally, with what little UV light it does see there is a reaction of sorts kind of like oxidation. The certain chemical(s) will then discolor giving us the results we see.

 

[mbrick]

I believe that. So you're saying it is inevitable with age, and not reversible. Bummer...

 

[Pro-pulsion]

Unfortunately yes, but that is also why under the tank straps it takes so much longer to fade. The tension of the straps somewhat seals that portion of the tank from atmospheric exposure. With the quality of fuel these days...or rather lack of...and being oxygenated, depending on if the fuel has ethanol blended it could speed that process up. I know from an old couch I used to have and hate lol, about 7 years ago when it ran the fuel then stripped the inside of the tank and lines plugging the little filters inside the Mikuni carbs.

 

[mbrick]

Ah, the infamous gray line sea-doo...

 

[Pro-pulsion]

Notice how I chose to leave out the name it was like a very bad relationship...you just want to forget everything about her lol.

 

[mbrick]

I replaced the lines on one myself recently, and just in time. Based on the small Mikuni carb screen being nearly clogged, it was not far from a lean seize.

 

[Pro-pulsion]

I had every gremlin possible with mine. Fuel tank, lines, electrical, crank bearings, full rebuild. I owned for 5 years and could only ride it about 4 times, the rest of the time it was in limbo for repair. Worst machine ever. Watch those crank bearings like a hawk. My indicator was when I would crack it full open. The battery light would come on until I let off. The crank bearings were destroyed allowing the crank to move up and down. It would not only open an air gap between the seals and throw off my fuel mixture running it lean but the movement was so strong, the stator cup would contact the stator and burnt out my stator.

 

[mbrick]

That sounds awful. Yikes...

I forgot to put the drains in one time and sunk it right at the dock. Quickly pulled it out and onto the trailer, pulled the spark plugs, got the water out of the engine, and then got it running. Last time I'll forget the drain plugs, felt like an idiot!

I rode it for a long while after that to get it hot and well oiled. Been fine since

 

[Pro-pulsion]

Lol...it was a surefire way of making the decision for me to never again purchase or even look at that brand with anything less then pure disgust. That same year I decided to give it one more chance back in 06, I went to our closest local dealer to price out parts and what do ya know...that product line just so happens to stop parts support for all of their craft after it reaches 10 years of age. Then they gave away the secret about 5 years ago in one of their pwc commercials..."built for a decade of fun" they said lol. Evidently they left out built to be obsolete after only a decade lol. Never again! Worst.Product line.Ever.

 

[tntsuperjet]

The gas and oil combination causes the tank to yellow
My 1991 440 super stock has only run Sunoco standard and Dumonde tech racing castor and the tank is still as white as the day it was purchased.
My 92 sN was perfect till I put pump gas in it 5yrs ago now it's brown.
If you scrub them hard with comet they come back some.

 

[Big Kahuna]

Simple green works also.

 

[SkiPro]

Has anyone thought about soaking one in a bucket of 1/3 water to bleach ratio?
Or scrubing the Sht out of it with some comet or ajax?

 

[DAG]

The gas and oil combination causes the tank to yellow.

This is what I would assume too, but.... why don't the tanks yellow under the straps?

 

[Big Kahuna]

Has anyone thought about soaking one in a bucket of 1/3 water to bleach ratio?
Or scrubing the Sht out of it with some comet or ajax?

2 post above yours Tim said "If you scrub them hard with comet they come back some."

 

[stuntbikemike]

If you ride hard you tank starts to get scared hence the yellow. Just my opinion.

 

[Pro-pulsion]

If you ride hard you tank starts to get scared hence the yellow. Just my opinion.

Hah! Sounds like the aforementioned brand of couch I regrettably once owned...except it was scared to see life so it was built yellow lol...or as some folk refer to it...yellar

 

[Pro-pulsion]

This is what I would assume too, but.... why don't the tanks yellow under the straps?

Unfortunately yes, but that is also why under the tank straps it takes so much longer to fade. The tension of the straps somewhat seals that portion of the tank from atmospheric exposure.