without the blade will it go up higher?
do you have the draft control set straight over ( up ) for position control?
with the blade on and it pulsing, and the hydro fill cap off.. look in with a strong light and see if you have fluid pouring out the mouth of the cyl.
the pump only makes 4gpm max.. if the load is heavy and the leak bad... well..
lift cover gasket and oring kit costs a whopping 15$
might also have a worn cam follower pin and / or cam surface. pin is repalceable, cam can be built up with weld and reground... it usually wears in profile and leaves a witness mark to weld back up.
pulsing is leakdown and circuit regen.
if it lifts higher with no load.. it's a bad leak.
if it does not lift higher, then the lift is out of adjustment.. most likely due to a very worn cam pin / cam...