If you have an early version of the .40 FP, you will need to run a fuel with castor oil and run it very, very rich for the first 45-60 minutes. The early versions had the iron alloy piston running in a steel liner, and they'd take a while to break in. Once broken-in, though, they were super, super engines with ultra-reliable running habits.

You can tell if you have one of those if they tend to quit as soon as you try to lean it during the first 10-15 minutes. They did not at all like to be run with fuels that had all-synthetic oil packages.

Starting points are 2-1/2 turns out from closed on the high-speed needle, and the air-bleed screw set to block the air-bleed hole 1/2-way. You then adjust as necessary.