85 Gs 700 won't stay running

[Ickaruz]

No crud

Thanks for the advice but there is no crud. There is definitely a vacuum issue in the sense that the tank don't vent and therefore the gas just slows to nothing more than a trickle if that when I open the petcock to direct feed.

[Dogma]

This flow test has complications, as the flow should naturally slow down as the fuel level drops. Basically, more gas will come out of the petcock when there are a couple gallons of fuel sitting on it in the tank. When the tank gets low on fuel, there is much less hydrostatic pressure pushing fuel into the petcock. This is why in-line filters can be a problem.

If I were doing this test, I'd time it draining with the cap vs draining without. There should be only negligible difference. Of course, if the flow stops, there is a problem.

One thing I'd like to know, just to be sure: To initiate flow, did you have to do anything other that turn the petcock to prime, or did you also have to suck on the vacuum line?

[Ickaruz]

Flow

There was a major differende when I popped the cap off. in itally with cap on it started flowing by itself when I turned petcock to prime, however, that soon slowed even though there was still plenty of fuel. I mean to say it slowed noticeably within thirty seconds. Then I popped the cap off and the flow resumed steady and strong. So i'm hoping now that that settles it and the problem is venting, which I have no idea how a tank vents. I understand the idea but as to where I need a little help..

[Dogma]

Ok, that sounds pretty conclusive, then.

For the vent in my cap, there was a little ball in a chamber that made a check-valve which should close if the bike tips over. If you take the cap apart far enough to get into that, you should see where the vent passage goes from there. Assuming of course, that yours is similar to mine.