Thanks for the replies; HF Farms that's a good point, I double checked the gasket just now and there is indeed a cutout for that passage by the butterfly. It has a new insulator base so I just checked that for flat with a machinist straight edge, can't see any light on either side (flat). Resinstalled, no change.
Rasman - Yes it ran at idle. I fully agree, and I'm trying to nail it down hoping someone's had a similar misadventure. I haven't rebuilt it (yet) only cleaned it out, the gasket for the top part didn't tear and I happened to have a new gasket for that base to bowl. Checked them for flat as well. All the passages blow clear which is what's driving me nuts, if the main jet was plugged I could see this happening. The idle passage from the main jet in particular, is free right from the jet down to the cast iron base. I've pulled it apart several times now and check that every time.
Original fuel pump, only the tank and lines were replaced. Fuel feed is fine and with the original pump, the pressure would not have increased.
Highly annoying. I'm guessing vacuum leak but would assume the thing would still run - even choking it out won't allow it to draw fuel into the intake from the bowl. Dribble some gas in there, it starts right up. As I say, hit the throttle and fuel squirts out. But it will not come out from the idle circuit. Again, importantly, there is fuel flowing into the bowl (i.e. the needle is not stuck); float level is correct.
It will indeed be something obvious when I find it....
