2 Fuel Valve Questions

[tulsawalk]

I run an MSF school and have a bunch of GZ250s in the fleet.

Questions:

1. How much of a stream should I have from the fuel hose when applying vacuum to the fuel valve vacuum line?

2. How many inches of vacuum are required to open the fuel valve and let fuel flow?

[blaine]

Welcome.It takes only a small amount of vacuum to open the fuel valve.Fuel flow should be fairly strong.Why not just put the petcock on "pri"? Or are you trying to determine fuel flow in the "on" position?
:cool:

[tulsawalk]

Want to fix the problem. Have had to do 3 oil changes this year for GZs left in prime. Having to do the clutch friction plates now on one that filled with fuel twice.

Bike doesn't want to run on prime for very long either.

I removed the tank so I could work with it on the bench. When turned to prime fuel runs freely from the fuel line. Full 1/4" stream.

When I draw a vacuum on the valve using my mouth (forgot to take my mighty vac with me) I have to draw pretty hard and get only a very small stream, more along the lines of a heavy drip. Yes, I've checked, there is nothing clogging the vacuum line.

What are the symptoms if the fuel valve is bad? I assume there is a diaphragm in the valve.

[blaine]

Pull the petcock out and check the screens for dirt,that will stop flow of fuel.
:cool:

[tulsawalk]

Well I answered my questions with some experimentation and another GZ (I have 8 of them) and thought I would share them.

Fuel stream should be full when the valve is opened with vacuum in either the on or reserve position.

It takes 2.5 - 3 inches of vacuum to operate the fuel valve. i determined this using my mighty vac and the tank off of another GZ without a fuel feed problem.

[Gz Rider]

...