4 New fuel-tanks in one year on Jonway El-Ninjo

We bought two brand new scooters in 2014. One a galactica and an El-ninjo 150cc.<br> There is a design error on the El-Ninjo. Its fuel-tanks keeps on leaking and cracks down the middle.<br> Bike has just over 700 Real Km's on the clock and in perfect condition. Not a scratch.<br> How is it that the fuel-tanks only lasts 150km?<br> The local supplier through whom i bought it, tried everything he could. The bike travels maximum 2km per day on normal roads.<br> All i get is that the guarantee doesn't cover fuel tanks or anything else really. Is the product quality so bad that it cannot be guaranteed? What on earth is the problem with this bike? The boy driving it weighs roughly 70kg.<br> I simply cannot continue buying new fuel tanks!