Old Kirby brushroll question

[captchar]

so I have three Kirbys in my collection, a 509, 519 and a Heritage II Legend, my question is how do I properly adjust the brush roll, eg how much brush should be sticking out of the nozzle if any? as the generation series onward use a 4 notch brushroller, older style had set screws

 

[texaskirbyguy]

Rule of thumb - 1/8" of bristles should protrude from rug plate.

 

[captchar]

thanks that would make sense why my 519 wasn't picking up at all, as there was no brush at all protruding out