petcock bad

Hi All, My 83 Maxim did not have a vacuum tube attached to the petcock when I bought it several months ago. It ran, however I'm not sure how well it did since I have no reference for comparison. I rode it for short distances to the gas station and such a few times. There have been several...

Bike runs great when the petcock is on reserve but in the "on" position it will idle rough and if you try to rev it or ride it anywhere, it'll make it a couple minutes barely running and die. (fuel level in the tank is nowhere near low) I'm wondering if the petcock is clogged in the "on"...