gotta simple petcock question

[allisonmo2]

i just picked up an 81 xs1100 and the petcocks say res. run. and pri,

what is the pri. for? i assumed the reserve is just that and run was the main tank. what is pri.?

thanks.

[chevy45412001]

pri

prime ,runs fuel all the time. used for me after carb work to fill the bowls with fuel. the other positions only work when the motor creates vacum . prime will work all the time (no vacum needed).

[allisonmo2]

thanks.