Having trouble tuning your carburetor, than this might be the solution. This fuel reservoir is positioned between the fuel pump and carburetor. It works as a fuel gravity feed system. This relieves too much fuel pressure from building up in the carburetor. Too much fuel pressure can make it really hard to fine tune your carburetor as it adds more pressure to the float and needle/seat. Any unused fuel is returned through the second nipple via the return line and back to the fuel tank. The bottom output must be directly connected with the carburetor. The reservoir should be placed over the float bowl of the carburetor, in a vertical position. Note that there is no fuel filter inside the reservoir.