PMO Carburetor help needed. Options

[defianty]

Some of you may have seen my build thread where I mentioned I stripped down my PMO's for a good clean. Sitting around for a couple of years with remnants of old fuel in didn't do them any favours.

Now all clean and back together I'm having an issue I can't find a solution to and I need help.

So with everything installed back on the car and connected correctly - when the car starts it instantly idles at 4,000rpm+ rather scary! So it's switched off immediately.
This has absolutely nothing to do with the idle adjustment screws, the throttle linkage or the accelerator cable - they're all disconnected.

Yesterday whilst trying to troubleshoot further I confirmed the fuel pressure is correct at 3.5psi from the PMO fuel regulator so I thought I could rule that out. However when I then tried to recheck the timing with the fuel pump disconnected the car fired up and straight away and idled at 900rpm fairly smoothly with the fuel in the bowls and continued to run well until the fuel ran out. Fuel pump back on - bowls filled - restarted and back to a 4,000rpm idle.

Any suggestions welcome!