83 kz650 csr

right, just picked it up, few problems. when starting, the switch that goes between res pti and yes for the fuel line leaks like a bat out of hell, or leaks like that when on pti. at least i believe its pti... otherwise it seems to be fine. whats up with that?

The fuel valve on the tank (petcock) should have 3 positions: RES, PRI & ON.
RES - Reserve; used when the gas level gets low, the engine will start to sputter, gas light may come on if it's working, you should switch to reserve and fill up soon.

PRI - Prime; used to prime the carbs. In this position gas will free flow, filling the carbs if needed. I usually set the petcock to prime for a few minutes if I haven't riden for a few days, then turn the petcock to ON.

ON - Normal position when riding and having a fair bit of gas in the tank.

In the ON & RES positons gas will only flow if the engine is running, creating vacuum through the smaller vacuum connection line to the petcock and opening a valve in the petcock.

If you have a leak, check that the gas line and vacuum line connections are tight, or that the two screws on the front of the petcock are tight.
The petcocks do wear down over time and leaks can develope. You can buy the inner parts and rebuild your petcock. Probably over 75% of those who have tried rebuilding their petcock still had leaks afterwards, and ended up buying a replacement.