You have two levels of filters on your petcock. the higher filter draws when you have it in the on position, the lower filter draws when you switch to reserve.
That is why the bike sputters when you furst get low on fuel. The "on" filter no longer has gas it can draw on, switching to reserve opens up the lower line and filter.
You have three positions on the petcock. Lookung directly at it they are
off, on, reserve.
In the off position the lever is pulled back toward the rear and both lines closed off. for In the lever is straight down and the higher line open, for reserve the lever is swung towards the front of the bike and the lower line opened.
Hope that helps.
(one small note.. the earlier models petcocks did not have an off position, they had Pri (for prime) On and Reserve. For your 92 it should be Off, On and Reserve though(
Patriot Guard Rider
2000 VN750 Sere (Serendipity)
1990 GL1500 (Ole Blue)
1986 VN750 EVie (project bike, heavy custom)
VROC # 11628 / 25000-H
ARVROC # 12 Coordinator and Crowd Control
OKVROC # 18 (H)
TNVROC # 45 (H)