[whatitstrue]

Originally Posted by flynjay

There are two hoses attached to the fuel tank petcock. One is the fuel outlet (larger) the other is the vacuum line (smaller diameter).

First check - normal engine produced vacuum is opening the petcock valve:

Turn the petcock valve to OFF.
Remove the hose from the fuel port (larger), some gas will come out so be prepared to catch it with a glass jar.
Turn the petcock valve to ON or RES.
Thumb the starter for 5s or so, be ready to catch the gas coming out of the tank. Fuel should come out of the tank in pulses.

Second check - Vacuum diaphram is intact and working properly:

Turn the Petcock to OFF.
Pull the vacuum line of the petcock and attach a hose to the vacuum input (smaller).
Manually apply vacuum to the hose (suck on it equivalent to drinking water through a straw). Too much vacuum could damage the diaphram. You should only be able to suck for a little bit and feel resistance.
If you don't feel any resistance STOP. The petcock diaphram needs to be replaced.
If you do feel resistance, continue.
Turn the Petcock to ON or RES.
Apply vacuum again, this time be ready to catch the fuel that comes out of the other port. Fuel should flow at a pretty good pace.

If either one of those doesn't flow gas well then you need to clean or rebuild the petcock. Also, there are fuel filters inside the tank attached to the inlet tubes (on my bike at least) so those could be clogged as well.

If the bike has been riden recently and starts back up after it stalls I doubt it s a fuel delivery problem. Sounds more like its not properly warmed or inproper fuel/air ratio?