Hi my name is Gordon and i have a slight problem with keeping the oil in the oil tank. Theirs a oil line that runs not from the oil pump but from the engine just above the oil pump and returns to the top of the oil tank.Should this oil line have some soft of breather system on it to releve pressure in the oil tank

 

That line IS the oil tank vent.
It vents back to the crankcase. It could be restricted or if it's overfilled with oil, that can cause the problem. Also, not certain exactly where that models crankcase vent is, but if you know or can find it, it may be restricted or plugged.

 

Do you keep adding oil to the tank? If so and your engine doesn't leak oil you could be wet sumping which is where the oil won't return to the tank because a feed/return/vent line is clogged OR the check valve in your oil pump (if you have a check valve) is stuck open. Either one of theseconditions cause oil to stay in the engine rather then return to the tank. Most people think they are low on oil and keep adding untiloil starts blowing out the breather tube in the air cleaner. Clean all your oil & vent lines (make sure none are crimped or bent)andthe check valve and see if it happens again.