Fuel Flow Issues

[5150bossman]

So I have had a recurring problem for the past couple of years that I can't seem to track down.  On several occasions, the motor stalls when we are in a nose down attitude and the pump has to pull fuel up to the motor.  It can happen going down a rough trail, or even on the street if the road is long and steep enough.  If we are level or nose up, there is no issue.  Looking at the fuel filter between the pump and carb when it stalls, it looks as if it is completely empty (not even a little bit on the bottom to touch the filter element). There is fuel in the tank, and the pick-up tube remains covered with fuel.  I thought it was bad rubber fuel lines (even though no signs of leaks), so I have replaced them, twice.  I just put a new stock fuel pump/push rod on it.  The push rod measurements seem to be right. I still see bubbles entering the filter now and again (mostly when the motor is warm) between the pump and the carb.  Is this normal?  The carb is a single Weber 40 which was rebuilt last year and runs well.  I have the float level set at 10 MM per the Weber Carb book. Could it be a leak in the hard line through the tunnel (again, no signs or smells of a leak that I can tell), or maybe vapor lock causing gas expansion, or the carb float not set right?  I'm not sure where to go from here.  Any suggestions or insight would be greatly appreciated.

[1856]

Mike you might check the float level again? Does it seem to be loading up (rich) or starving (lean) when it fails?

I have had similar problems with Webers. I've been setting them at 17mm for off road... and when it gets really steep we control the fuel level with the elc. fuel pump (like dry sumping)

MnC

[5150bossman]

I rechecked the float level, and it was actually 12.5 (Which is what Redline Weber recommends for off-road use). As it seems starved for fuel (not flooding), I reset it for 10. We will be out this weekend, so we will see how it runs.