Gas tank petcock acting funny

[NacsMXer]

On my gas tank on my 400EX, when I turn the selector down to the ON position gas just sort of trickles out slowly. When I turn the selector up to the RESERVE position, gas flows out freely as it should.

Is my petcock valve bad or what? Anybody know what this is an indicator of? Thanks for your replies.. :)

[GPracer2500]

There's a very fine screen on the pickup tube for the ON position. This pickup tube is the part of the petcock that extends up into the tank. Unbolt the petcock from the tank and the whole assemply will come out. I'd guess there's probably some gunk clogging the screen.

[NacsMXer]

Originally posted by GPracer2500
There's a very fine screen on the pickup tube for the ON position. This pickup tube is the part of the petcock that extends up into the tank. Unbolt the petcock from the tank and the whole assemply will come out. I'd guess there's probably some gunk clogging the screen.

Ok thanks i'll try that, I appreciate the input. I assume that the reserve circuit bypasses this screen altogether...hence the reason it flows freely in that position?

[GPracer2500]

Hmmm. Good question--made me think about this a little harder. ;)

I believe the RES does feed through the same screen. The ON feeds through a tube that runs up inside the screen maybe two inches or so. The RES feeds straight through to the petcocks "base"--but it's still on the filtered side of the screen. The screen is a tube than can be pulled free from the petcock base. Once the screen is off you'll see the ON pickup tube and the hole that feeds RES.

So, sounds like maybe it's the pickup tube for ON rather than the screen that's clogged. Might even be a clog somewhere inside the valve assembly of the petcock. They're pretty easy to disassemble for cleaning--if that's necessary. You might try just blowing through the petcock in the ON position with a little compressed air while it's out of the tank.

[NacsMXer]

I see now, thanks for the thorough explanation. I'm sure it will make much more sense when I get a chance to tear it apart and see what's going on in there :p