hoganter post=34121 userid=2512
...I had replaced the original jec fuel pump with a walbro, however its too high capacity or volume for the new vacuum petcock or fuel valve, as it pumps 150 litres per hour.
I was getting bubbles in the return line.
Been looking hard for another pump that is a lot slower than the walbro...
Good luck
Hello Hoganter,
I also ordered a fuel pump for a Moto Guzzi, this one from MGCycle.com. Got it for $56.00 including shipping. I haven't yet installed it as I found a way to slow down the Walbro 393, at least for now. I contacted Walbro twice with questions about which of their pumps would work best for my ZN. No Joy and no help there.
I agree with you that the intake flow with the Walbro 393 is such that it causes cavitation after the vacuum operated petcock. The unknown is: Once the fuel gets to the pressure side of the pump is there enough time and pressure to condense the bubbles back into liquid so that the injectors can do their job properly?
I asked a old coworker of mine what sort of speed controler would work best to slow down a DC brushed motor. He suggested a potentiometer. Two iterations later I managed to drop the dead head pressure from 85 PSI to 50 PSI. I realize that the dead head pressure is not a measure of fuel flow but the agitation I see in the fuel filter is much reduced as I have it set up presently. I could go further but I'm satisfied for now. The bike stumbles a bit off the line but pulls hard from 3000 RPM. I'm hoping that adjusting the throttle position sensor will help, if not I'll put the air box back on so as to get to a valid base line.
Regards
Bill
