Fuel Delivery Issue

Hi guys, GPz750 A1 is almost running.

I have successfully rebuilt the carbs over a few weeks. I have also put the carbs back on the bike and connected the throttle etc.

My main issue is I have no fuel being delivered when I hit the starter. I tried this with and without a tank on (bypassing any petcock issues)

Vac Line
I have tested the petcock - it gushes petrol when in prime and the fuel hose is disconnected. However, the fuel stops immediately when either turned to ON or RES (with the vac hose connected). I can feel a little pressure when I put my finger over the vac hose.

Fuel Line
The fuel line is not obstructed in that I can physically inject fuel down the line and it appears in the clear fuel filter. The fuel trickles out of the fuel filter (gravity) and almost makes the bike tick over when there is enough fuel and the starter is hit.

Overall
However, when the tank is on, petcock is set to ANY position, no fuel seems to come down the fuel line (it doesnt appear at the fuel filter).

What is going on? (Breather hoses are conneccted on the outermost carbs btw)

Do you have an obstruction in the carbs where the fuel feeds in? Or a vacuum problem, but that wouldn't explain why the fuel doesn't feed in prime...Is it a new fuel filter? Stupid question here, is the fuel filter installed backward (I only ask that because I've done it myself).

Nevermind, the beast has awoken!!!!!!!

WOOOHOOO!

Theres a bit of white smoke, but it sounds like a rocket :woohoo:

Same issue with no fuel delivery for me. Have a '78 KZ650 C2 basketcase that's resurrecting. Cleaned the pitcock well, replaced the diaphram cause the old one leaked out of the side. Presently I don't even have fuel delivery when in the prime position. Fuel is getting to the diaphram but nothing afterward. How can I rectify the problem.

Did you put the diaphram in correctly when you rebuilt it? If the petcock isn't plugged before hitting the diaphram but you're not getting fuel past the diaphram that's where I'd look.

The diaphram can only go in one of 2 ways. There are a couple of plastic nipples that fit into recessed holes on the pitcock body. I've tried it each way. Shouldn't the prime position allow fuel to flow freely past the diaphram and through the pitcock?
JK