If it "spurts" alot it would indicate that the primary seal is not in good condition.
As you move the lever initially, it should firstly close off the route to the reservoir and so direct the fluid down line to the caliper.
If this first action is slow or impaired, then the fluid starts to come back into the reservoir, giving the spurt. Also, a longer lever travel in use.
Severe wear of this makes it difficult to bleed the system as well.