Zenith carbs: Hideous things. Went through 2 sets. Warped quickly and badly and ran rich . In 1998 When I restored my wife's '70 250C she's owned since 11/70 replaced them with Webers from Jam Enineering, Monterey, CA which makes a total kit set & jetted specifically for the M130.923 engine. My mechainc bolted the kit on adjusted some settings and I drove away quite satisfied.

Result: trouble free, and an engine at idle that's almost as smooth as an injected engine.