Never heard of such going soft on them, although they may be thin and quite flexable, they were that way from new. Worst I have heard of from the ethanol is it may make the tanks expand and grow, making fitment difficult. In that case, remove to air out for a while.
What is the problem with it anyway?
the bikie will never run like the little gas gas because the cylinder porting is more aggressive. You may retard the ignition timing by 2-3 mm.
the dellorto fuel screw is not sensitive. run your 35 pilot and 118-122 main, turn the mix 3 turns out and try it. they are reliable carbs, just not precise carbs!
if really cold they can be a pig to start. lay the bike over on the left handlebar for a few seconds to allow it to flood the carb a bit.
Contact Steve at Motoplat UK to fix them, but you will have no way of doing dynamic testing short of replacemrnt as the triggers seem to be the culprit..
