Testing the petcock for problems?

[Watevaman]

 Finally have some time off today so I'm going to look over the GS and see if I can figure out why I was getting gas into the oil. I was reading over this thread:

http://gstwins.com/gsboard/index.php?topic=58926.0

and saw the post about possibly the gas overriding the vacuum diaphragm and flowing into the carb. Looking at this picture:



which hose should I remove to see if gas is bypassing the petcock with the engine off? I have the tank off right now, so would using a funnel and some gas attached to the main ON fuel hose work the same as long as the funnel is the same level that the tank would be?

Thing is, this guy's bike wasn't running at all, whereas mine was running fine and that's why if this goes well I'm going to check the floats.

[craigs449]

Pull the vacuum lead that goes to the right hand carb (on a 2001/2002 model).  Turn the tank petcock on, turn the main petcock to Prime, then to on, then to reserve......you should NOT have any fuel coming from that line in any of these petcock positions...if you do, the vacuum diaphram is messed up. Also, after you do this, hook the vacuum line back up, them pull the supply line coming from the petcock off and turn the main petcock to "on" and then "reserve"...if you have fuel coming out without the bike running, the petcock is bad.  The "On" and "Reserve" positions should only provide fuel when the bike is running or starter is cranking.........

[adidasguy]

Fuel WILL come out in PRIME. The PRIME position bypasses the vacuum so you can get fuel unto empty carbs without the engine running.

[craigs449]

Fuel WILL come out in PRIME. The PRIME position bypasses the vacuum so you can get fuel unto empty carbs without the engine running.

Fuel will NOT come out of the vacuum line with the petcock in any position, including "Prime".  Fuel will, however, come out of the fuel supply line when the motor is off and the petcock is on "prime"......Just sayin'

[adidasguy]

I guess it implies the vacuum line. It doesn't really say fuel will go through when in prime. It was a little vague the way it was written.

You can test a petcock or "pet chicken" (love that filter!) with some clean hoses from homor despot, water, used drink bottle and you can suck on the vacuum line and test everything in your kitchen.

You can blow through the fuel lines and see what happens in the 3 positions. Blow lightly, and air goes through only in prime. No air should go out the vacuum port. Blow harder and you can force air through the proper lines in ON or RES positions. The vacuum valve might resonate like a bad saxophone. That's OK - means it is working and not leaking.