I recently bought a running 85 VF500 that Im trying to sort out the diaphragm and vacuum hose setup on the petcock. First I guess is does anyone know what the diaphragm does? Is it adding pressure to the fuel line? Second the petcock has three nipples. One is the fuel line and the other two are the vacuum line to the number two cylinder and the other is an air vent? My problem is when the engine is warm and I hold it steady above 5-6,000 rpms it seems like its not getting fuel. It runs great but theres a hesitation, consistently, every couple seconds. Almost like I took my hand off the throttle for second then it goes back to normal. Right now the vacuum lines are just capped off. If I take the caps off fuel pours out like they're fuel lines. If I replace the diaphragm and get the vacuum line sorted out will that get more fuel to the carbs? Or is it more likely the float levels arent correct? I just used a ruler to set them but they should be close. Also it runs great when its warming up so thinking they should be fine.