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Why do some petrol tank change colour

I have 2 ty monos  and one of them has changed from white to a faint rust colour ;).

I have noticed it is not only Yamahas that do this.

is there something that can be done to prevent this.:wall:

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I think its the Petrol that does this . I don't know the proper scientific term for it { but I am sure someone does, and will be along shortly}

its as if the plastic is porous and the petrol soaks into it.  

  Perhaps different types of Petrol and the different Premix oil cause different effects / colour changes ?

and of course could be explained by different types of plastic being used to manufacture two tanks that look the same ?

as for prevention, I guess you could get a new tank and fill it and drain it on the days you ride without leaving petrol in overnight  may work ?

 

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Common answer is petrol but if you look at the underneath of the tank is that discoloured too? Usually not, my SWM tank was still perfect yellow underneath and also under the tank badges if they were removed, whereas all surfaces touched by sunlight went darker.The entire tank surface should be affected if it's caused by petrol shouldn't it? Ultra violet from sunlight discolours plastic, just look at garden furniture or kids toys like slides, plastic bikes, swings etc.  If these tanks seeped petrol vapour like they're said to, if you left one in a closed garage for any length of time it should reek of petrol, so why don't I smell any?

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3 minutes ago, woody said:

Common answer is petrol but if you look at the underneath of the tank is that discoloured too? Usually not, my SWM tank was still perfect yellow underneath and also under the tank badges if they were removed, whereas all surfaces touched by sunlight went darker.The entire tank surface should be affected if it's caused by petrol shouldn't it? Ultra violet from sunlight discolours plastic, just look at garden furniture or kids toys like slides, plastic bikes, swings etc.  If these tanks seeped petrol vapour like they're said to, if you left one in a closed garage for any length of time it should reek of petrol, so why don't I smell any?

I agree that ultra violet must be a major factor,  however they definitely seep vapour as stickers last days rather than weeks before falling off. 

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2 hours ago, b40rt said:

I agree that ultra violet must be a major factor,  however they definitely seep vapour as stickers last days rather than weeks before falling off. 

The bubbles that form when people paint these tanks are also an indicator of something permeating through the plastic

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Petrol vapour is lighter than air so naturally travels upwards. The underneath areas of a plastic tank are usually warmed by the heat from the engine thus encouraging the petrol vapour to rise more so. Certainly the suns rays can affect the plastic if exposed for long periods of time but it is mostly the staining from the petrol that discolours the plastic petrol tank. If anyone has an old red plastic fuel can  by now it should be verging toward a pinkish discolouration. The green unleaded plastic fuel cans seem to be able to retain their ‘greeness’ for longer. Potentially if you filled a stained tank with a strong bleach mix (70% bleach 30% water) and left it for a few weeks you may find that some of the staining goes, but its not a definite cure. 

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2 hours ago, b40rt said:

I agree that ultra violet must be a major factor,  however they definitely seep vapour as stickers last days rather than weeks before falling off. 

Think thats more to do with the adhesive on the stickers and the suitability of the plastic the tank is made from. Some plastic mudguards will not take stickers well, thats some not all. The plastic cutting boards that make good number boards and mud deflectors will not always accept stickers, you clean and prep the surface, apply the sticker and hey presto it starts to lift off after a few minutes...annoying. Duct tape seems to be the only material that grabs hold. When you look closely at the tanks that repel stickers there appears to be a slight blemished surface, whereas tanks that readily take stickers have an almost perfectly smooth surface a bit like polycarbonate helmets or workmans plastic head protectors.

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UV damage plays its part, as does fuel permeating through the tank, & cack handed fill ups, spilling fuel over your lovely "decals !!!".

So.......  what can you do about it.  Plastic tanks are quite thick, robustly made can be easily refurbished. Layers of Uv damage can be scraped off, wet flatted & brought back to life with a Car body polishing mop & compound.  TY Mono & Fantic tanks come up surprisingly well.Don't go down the heat gun or repainting route though , as it doesn't work very well. Its all there on You Tube. Our friends across the water are experts at it BTW !!!.

Once tank has been refurbed to your satisfaction, Do this :

Use better quality fuel i.e V - Power, as it has less of the low grade additives in it such as ethanol. Avoid Supermarket fuel too, as it is generally at the lower end of the fuel quality spectrum.

Take a bit of care when filling up, wipe off any spills ASAP. Your decals will eventually come off, so get your local graphics shop to copy & knock up a few spare sets.

Drain tank after every ride & leave fuel cap off.  Tank will be dry. (not so good if you use bike all of the time).

Don't use old fuel. Modern fuels are not long lived.

Works for me & I have a few olde worlde  classics with Fibre Glass tanks.  

   

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18 hours ago, section swept said:

Think thats more to do with the adhesive on the stickers and the suitability of the plastic the tank is made from. 

I'm sure that's true of many plastics, my experience is with Acerbis tanks and guards. Identical stickers will last till they wear away on guards, but lift rapidly on tanks. 

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My brother had his 199a tank painted. I warned against spending the money,but you know how little brothers can be. Anyway,that was about three years ago and it,s still holding up no bubbling.The decals were put on this past summer and so far have not lifted or bubbled.The painter used an apoxy primer used for plastic car bumpers and I,m thinking that is why it,s holding up.                                                                                                                                                                                                                                                                                             My 199a was rattle can painted and it and the decals are bubbling pretty bad.They both get drained with the caps left off for a day or so after every ride.

 

EB42C5CC-2EC0-4CB6-AD58-24D413432EC8.jpeg

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On 1/11/2019 at 11:23 PM, scot taco said:

My brother had his 199a tank painted. I warned against spending the money,but you know how little brothers can be. Anyway,that was about three years ago and it,s still holding up no bubbling.The decals were put on this past summer and so far have not lifted or bubbled.The painter used an apoxy primer used for plastic car bumpers and I,m thinking that is why it,s holding up.                                                                                                                                                                                                                                                                                             My 199a was rattle can painted and it and the decals are bubbling pretty bad.They both get drained with the caps left off for a day or so after every ride.

 

EB42C5CC-2EC0-4CB6-AD58-24D413432EC8.jpeg

Nice looking Sherpa and I like the Rebar quick lift stand.👍

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