Am now considering loading the bottom chamber full of Permatex 85420 fuel resistant sealant. This would force the needle/piston in the closed position and keep fuel from dribbling out the bottom of the assembly. And this sealant could be removed in future (unlike plugging it with JBweld, for example).

I can't imagine that a failed diaphragm is that uncommon.

Any ideas, anyone?

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Currently enjoying:
1967 250S - all manual with 4-spd on floor-- my Nifty 250