As mentioned in another thread I've been having quite a lot of trouble with the Plastic tank swelling on my M1000. It's a well known issue with Plastic tanks from various manufacturers, and the only cure appears to be airing it for a few months without any fuel in, so having two tanks I've been swapping them out every 6-12 months. I really don't like the thought of trying to coat the inside, as whatever you put in is REALLY hard to get out again. A couple of years ago I brought a rough tank, repainted it, added new Decals, then decided the Satin Black look I'd gone for wasn't actually that great, but have been using it on the bike as above. Then on Friday when the sun was out I tried to take the bike out for a ride and found the fuel pump had given up the ghost. I took my 999 out for a ride instead, but decided as the tank had to come off anyway, and the tank had swelled again, I might as well swap the tanks over. The tank on the bike was the original with the original paint. I must admit I was a little shocked at just how much bigger the old tank was this time, but unfortunately I think I've left it too long because the paint on the old tank has blistered really badly, even in places that don't always have fuel directly behind them when on the bike. I say blistered, but they appear more like pimples, and are hard. I've not tried too hard to pop any as I don't want to break the paint layer. Strangely they appear to be in lines in places:
Really shockingly bad manufacturing standards. You’d have thought designing a functional petrol tank would have been quite an easy task.
I’m not sure that is entirely fair on the manufacturer. There are a few things that could be at play here - - Plastics are always affected to some extent by certain elements in the fuel - their lifespan is not unlimited. They are certified for use with petrol but are not absolutely unaffected by it. - The tank degradation from the fuel is accelerated by other forms of age degradation (UV etc) so you sometimes see a tank suddenly get worse (and a N.O.S. Tank fail much faster than the original) - It is likely recent fuel in this tank had ethanol in it ( because it is not easy to get anything else) and the tank originally would probably not have been specced for alcohol long term - The repaint may have changed the way the tank can pass ethanol through it, so is lifting the paint differently to factory paint (which sometimes lifts like a snake skin) Nasher has taken a pragmatic approach - swap 2 tanks over at intervals. I guess the permanent fix is a hand made alloy tank. Big outlay, but if its a keeper…
In my head there is another option with an Ali tank, but I do need to put some more effort into working out if it will be significantly cheaper. To my mind the major expense of an Ali tank is getting the complex curves in place, welding the panels together and finished to an acceptable standard. The use of an English wheel and proper time served Panel beating skills on Aluminium don't come cheap. On the other hand, welding a multitude of flat Ali panels together to be fuel tight is skillful but quicker and a little easier to achieve. My TIG welding is not up to doing the whole job, but I could cut the panels and possibly tack some of it together ready. Then, I am very confident in taking a mold off a tank to produce a Fibreglass cover and finishing that to a high standard. A bit like more modern bikes.
My 2 quid jerry can made from plastic is 20 years old and can stand Ethanol without growing or shrinking or becoming porous. There's no excuse for these shambolic tanks.
Thank you John. The tank swapping works for me but is a bit of an annoyance. And yes an Ali tank would be nice. Just for the sake of accuracy, the tank that has the pimples is the original with the factory paint, not the one I've repainted.
Are you sure about that? Do you have a “control” unused can to check its dimensional stability against? Is it definitely not leaching volatiles out through the structure? Is it decoratively painted creating a barrier to free evaporation of these volatiles? Plastic tanks pass parts of the fuel through them - always have, always will - I’ve a KTM 500sx plastic tank from ‘92, started out white, went the colour of the 2t oil I was using practically straight away up to the fuel fill line, because it gets carried through the plastic (Castrol A747… mmmmm… now… where was I ? ) Jerry cans do it more, road bike tanks do it less (to achieve road certification) so its not really comparing apples with apples.
