Jasonp was right on the money. It looks like mine had fallen disconnected from the bottom of the left carb sometime, who knows when. So in theory, I've been running my bike with a non working nonmechanicalfuel pump and its done just fine 140 and below.

 

mine wont get fuel unless that small hose is hooked up . i hooked it up andran a hose to a gas can from my tank and the fuel pulsates out when i start the bike so it has some to do with the vacum from our engines so i dont see why you couldnt run the same on the older engines and eliminate the electric pump ??? does any one else know if it works?????

 

I'm confident that on any carbuerated bike, gravity feed is an option. I wonder why mine ran fine with the mechanical fuel pump inline and the vacuum hose not hooked to the carb. That really makes me wonder. I am going to experiment with the bike while it is apart. I'm going to feed it fuel with everything hooked up, then with everything minus the vacuum hose going to the bottom of the carb hooked up, and then with no fuel pump inline and see how the results vary.

 

Ok I've been playing with it all night. I've got som excellent video that will no doubt exceed any size limits in place on this forum. I may be able to upload them elsewhere but that's for later when I'm done. I need to start by correcting myself. My 1994 900rr has an electric fuel pump. With the fuel pump inline and all hooked up it runs fine. With the vacuum hose unplugged from the fuel pump (going to the bottom of the carbs) it runs fine, with the fuel pump unplugged the thing runs fine, with the thing completely removed and pure gravity feed from a small funnel through the fuel filter runs fine. These are all test runs up to 10k rpm while not moving. I wont be able to test my result moving until I geet my fiarings back from the body shop. I thought it was interesting that with the fuel pump inline yet unplugged the bike still runs fine. I'm going now to verify the operation of the fuel pump. Also the power leads going into the fuel pump were not sealed and when you blow into the smaller vacuum hose, you can hear air freely bleed through where the power comes into it. I have decided, at least temporarily, to seal it up with silicon and see what kind of difference that makes. I will post back more as I learn more.

 

Ok, There is a big performance difference in the tests with a fuel pump vs no fuel pump. I sealed up my pump real good with silicon around the rubber base and where the leads run into the pump then strapped it all in place. It runs very smooth and the pump runs 'on demand'. It pulsates about once a second at idle and it pulses at a faster rate as you give more throtle. When it was runnin with no fuel pump it had a tendancy to bog down. With the fuel pump, no boggage, if there was such a thing. I'm officially a fuel pump man. When it goes bad, i wont take it out, I'll buy a new fuel pump. Hope this trial and error helps.

 

Well, I'm messing wwith the bike again today, and I'm finding that it runs just fine without a fuel pump. One of these days I'll stop changing my mind.