Motorcycle Questions? Ask a Mechanic.
When you squeeze the lever fluid should shoot out of the bleed fitting on the slave cylinder. If not then there is a restriction somewhere in the system. If there is good pressure to the slave cylinder hose fitting then the restriction is inside the slave cylinder.
First try removing the bleed fitting to be sure it is not clogged. It is the first place that builds up rust and corrosion. You can usually clean it with a very small drill bit or piece of wire.