Farm Boss runs when held vertical but dies when when brought down to cut - Need

[Chauncy]

I have changed the fuel without any results.

[Caloren]

Cracked fuel supply line inside tank?

[John Mc]

Cracked fuel line is a good suggestion.

A couple more thoughts:

If there is a bit of a delay before it dies: The weight on the end of the fuel line fell off, or the fuel line is tangled or hung up on something, preventing it from dropping to the low side of the tank. (the delay would be while it runs out the fuel already in the line.)

If it dies as soon as you tip it, does this happen only at idle, and more likely to happen if it has been idling for a while?  If so, your idle mixture may be off (too rich at idle can cause extra fuel to build up or pool in carb. When you tip it, it floods and dies.)

[Cut4fun]

Check fuel line, fuel filter, tank vent, impulse line, carb diaphragms getting stiff.

[ladylake]

And after that report back   Steve

[joe_indi]

This could be caused by a sticky  check valve (jet valve) It allows air to enter the metering chamber, and lowers fuel level. The saw will run as long as the bar is parallel to the ground or pointing upwards. Because the fuel covers the jets. When the bar points down or the saw is held sideways the jets no longer have fuel to cover them, it is air. The saw then runs lean and dies.
My usual solution to this problem is open both bottom and top covers, remove the diaphragms. Take out the H and L screws. A bit difficult with limiter caps but a screw helps.
Immerse the carb for a hour in an emulsion of fuel and dish washing soap. Water at pressure sprayed into all visible orifices, a suitable syringe too works fine. Use an air blower to blow it dry and reassemble.Set the H and L rich to start up and adjust as required after warming up.