Tank painting/sanding and removal

So my GRiSO's tank is really ugly.. it was abused by the person before and now that I know it will run after I gut it all again and clean the insides, I want to do the tank as well. But I read up these are a sort of special plastic or something, so can these tanks even be sanded, and painted, or is it just a matter of sanding and wrapping? I've got some bubbles, scratches, and what looks like rust on plastic (which makes no sense to me) so what can I do other than buy a new tank?
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I'm not an auto refinished so I don't know all the steps but yes, of course you can repaint them!

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Chris,
The tanks are plastic -neoprene and don’t like ethanol gas. Ethanol will distort the shape of the tank. So if you don’t want that to happen again, you can hopefully use non ethanol and find that where you are. Or, you can line the tank with Caswell tank epoxy like I did about 8 years ago. If your tank is truly distorted (swelled from absorbing ethanol) it will go back to normal after sitting for some time (I think mine took at least 4 months). If it was me, I wouldn’t have it painted until I had a plan….. I’d be glad to talk you through the process I went through if you’re interested.

Hey fellas, I don't think my tank is warped, at least I'm not positive yet. It was just best up and abused, I might end up doing that lining you mentioned however since I expect the bike to be down for quite some time while I try and figure out how to get my throttle bodies disconnected from the bike for cleaning up. The whole engine blocks are coated in grime and oil too from when they weren't gasketed so I have a lot of cleaning to do

Hi all,
The effect of ethanol in these plastic tanks is a new information to me....
It seems that currently the 95 octane fuel in Portugal has 5% of ethanol. Is this concentration enough to cause problems?

Generally 5% (E5) is OK Matias, I regularly run 10% (E10) but try not to leave the bike idle with full E10 for long periods just in case - I've never had problems with tank swelling.

In reality it's impossible to know (it's based on fuel trading, closest refinery, availability of ethanol as blend component, blending schedule, blending economics etc etc etc) if the fuel you buy is E5 or E10 at max of ethanol content or not & E5 can even be sold as E10 since it meets/exceeds the spec.... I used to visit GALP refineries at Sines & Porto a lot !!

Either way best way IMHO forward for GRiSO is to keep tank level low if you are storing bike & add ethanol stabiliser ........BTW for my small block Guzzis I leave them full with E10 & no problems at all with metal tanks & carb seals/gaskets/fuel lines  etc all fine

Thanks Brian. Since 2018 the gas stations are obliged by law to indentify the pumps with the E level.
Why is idling a problem Brian, is it the heat?
I never noticed a swelling, but i did noticed one small bump on the paintjob that wasn't there before...(@John: one off those things that come with the age, you will say ,...)

Matias, I believe that by "idle" he meant parked or stored.

Perhaps. someday, someone will develop tanks made from a suitable material, not affected by ethanol. Moto Guzzi really dropped the ball on that one. But then, like flat tappets and dry bearings and crap electrics, it just adds to the charm.

When I bought the GRiSO it was with the intention of customising which included a repaint.
I used 2 pack automotive paint mixed to the colour I wanted with 2 pack clearcoat over it.
It's around 3 years now since I customised the GRiSO still loking good.

    Original

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   After painting

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