Water Softeners and Air Filtration Systems - Kenmore Softener not sucking Brine

I have an older Kenmore model 348491 that is not sucking brine. I have cleaned and replaced the gasket in the Venturi as well as all gaskets in the control head. I have not replaced the rotor disc. The unit pulls suction in the brine position but seems very weak. Not enough to pull liquid fully up the tube. Looking at the manual specs it shows a water flow of .6 liters per min in brine mode. Measuring the discharge hose I get about 1/3 of this. I'm guessing the low flow is not pulling enough vacuum. Should I replace the rotor or does anyone think the resin bed is plugged as a possibility? This unit is about 10yrs+ old and on City water. Looking for help. Thanks

there is another 'post' .
it states- chlorine from a city -water supply-has problems with the 'resin'-in the tank.
look around in this forum -till you fnd it!

Is there a flow control (black round rubber) in the venturi? If there is, remove it and the vaccum will increase. If not, replacing the rotor and seal (along with the fig 8 o ring) will help.

Thanks that seemed to work. I pulled the black plug and got good flow and suction. So in theory I should drill the hole out in this plug or will it work fine without it in place?

Just leave it out. For the life of me, I can not figure out why it is there.