Ok, back to basics.

What's your timing at? You can set your timing running at 1500 according to the book specs.

Did you set the idle mixture to the maximum vacuum? This could be a situation where you're running too lean.

Also there is an idle circuit that goes from the ventury through the idle screw to the top of the carburetor. If that's blocked it can also do the same simptoms as you're seeing.

Good luck.

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72 250 M130 W114