Starter button and igniter?

[Zanichbug]

Okay, fellas, and thanks for the various tips. I got the electrics working perfectly, and she turns over solid with a new battery. New starter button, and new solenoid, both actually old. If I turn the petcock on "res" and fill the bowls, she runs for five minutes, then won't start again. Vacuum problem? Petcock problem? Seems like she drains the bowls in that five minutes?

[Rich82GS750TZ]

if it's working properly, RES and ON pectock positions can't be used to fill empty carb bowls, as they both need vacuum applied in order to flow fuel. RES just has a lower draw point in the gas tank. If bowls are empty, you should put the petcock on PRI (prime) for 20-30 sec, then switch it back to RES or ON. That doesn't explain why your bowls are running dry though. Could be petcock malfunction. Carbs could need a good cleaning (see Ed Ness's BS (CV) carb rebuild tutorial on BikeCliff's website). Could be your gas tank cap vent isn't functioning, not allowing tank to draw in air needed to let the fuel flow through the petcock.

[rphillips]

Pet cock on PRI makes the fuel flow wide open, all the time, vac. or no vac. I'd put it on "PRI" & see if it starts, leave it on PRI. to see if it run OK in that position, then turn to "ON", If it runs OK on "PRI" then dies within a few minutes after going to "ON", you have a vac., petcock, or fuel level problem... Just my opinion.

[phydeauxmutt]

Are there two hoses connected to the petcock?

Are the other ends of those hoses in the proper places?