My 04 v-star runs rough if the gas is turned to on?

Question

if the gas is turned to reserve it runs good, but if it is turned to on, it will loose power, backfire, and die.

Answer 1

mags is almost right , fill it up when you run low ~ www.650ccnd.com  great website for modifying the bike , get fuel cleaner and octain booster from jpcycles

Answer 2

you are probably low on fuel...

Answer 3

take out the petcock and inspect it.  it may be clogged at the top