Im after some advice, I fitted a 2nd hand fuel tank as the original rotted out,but now can only fill to just over half a tank full,checked the breather hoses and all seem to be ok. should the main larger breather located just above the filler hose be submerged in fuel inside the tank, fuel can be heard bubbling when air is blown through it? there is also a restrictor in the top small breather line on top of the tank that i don't think my old tank had, is this meant to be there ? any help would be very appreciated.