E5 ate my Saturno - well, the carb float, anyway. The original Dellorto floats (some sort of plastic material) were eaten away and swollen to the point they wedged in the float chamber. Eurocarb were able to supply an E5 proof replacement. I'll find out in due couse whether it is E10 proof! The fibre washer between the tank and tap also disintegrated. This may have been due to E5, I don't know - it could have been due to old age!
E5/E10 causes some plastic tanks to swell. It does affect 1990s & 2000s Guzzis and Aprilias with plastic tanks, so it's pretty certain Gileras will be affected as well. They become difficult to remove/refit as the rear mount not longer lines up properly. I've left a Guzzi tank dry for more than 12 months and it did eventually shrink again. The fuel also permeates through the tank - there's no visible liquid loss on the outside as the process is very slow, so any fuel reaching the outside has plenty of time to vaporise. However, this does damage painted tanks, causing blistering of the paint.
The Nordie/RC600 carb has brass floats, so won't be so prone to damage (but maybe not immune) and the Nordie tank isn't painted, so fuel permeation won't be a problem.
If you've got plastic fuel lines, you may need to replace them with ethanol-proof rubber pipes. I've experienced plastic fuel lines disintegrating - quite literally - on several strimmers & hedgetrimmers and warnings have already been issued about using E10 in garden machinery, because of its severe effect on some plastic piping.
Given the Nordie/RC carb has an easily accesible drain screw, it seems sensible to drain the float chamber if the bike is not going to be used for even a short while. The shelf life of E5 can be as little as 8 weeks, so I will also be draining the tank and leaving the fuel cap off if the bike is going to be laid up!
