Buried In My Old Machinist Tool Box, I Bought This Spring When I Worked In Parts At An Alfa Dealer Over 35 Years Ago, This Part Should Probably Go On A Spider Veloce Or Sprint Speciale Restoration (#101.06.44.503.00), The Total Length Of The Spring Is Approximately 8-7/16", The Closed Coil Length Is Approximately 6", Alfaholics Has A Throttle Return Spring Kit (different design) On Their Website For About 15 Pounds, I Want Entirely Too Much Money For What This Part Is (a spring), However It Might Be Good Trading Material.
That spring would seam superflous. It accomplishes nothing relatice to closing the carbs..
I`ve never encountered one in 45 years of messing with this stuff.
With your issue of the rear carb not closing all the way the suspect spring is the internal one in the chamber between the butterflies behind the plate.
Since these carbs had the wrong syncronizing linkage on them when they were here for mods, you said you were going to swap to the old linkage from the 40 DCOEs. Are you sure you dont have the arm on that carb compressed against the body of the carb? Loosen the nut and see if that resolves the failure to close completely. They seemed to be fine with the aftermarket linkage on them.
Be sure the long rod is adjusted correctly. Too long and the long arm from the accelerator assembly will rest against the body/brake lines or other such clutter, preventing the linkage to return the carbs to idle.
Sometimes to get enough carb shaft motion to fully open the carbs, the shorter arm on the bell crank needs to be shortened to decrease the leaver point to get a higher % of motion on the arm pulling the carb open.
Uh Richard? I built the Webers and they both have new "race" springs. They slam shut with authority without the linkage installed. I'm pretty sure it's not the Webers. The spring discussed is not a Weber closing spring so much as a linkage "back-to-0-" spring. If the linkage is wrong, you can't close that rear Weber.
Just a thought. All I've done for you slam shut, don't they?
It is not a linkage problem. I disconnected it and the rear carb was not closing all the way. I synched the carbs this morning and it idled beautifully. But now I have a bigger problem - no compression, a damaged spark plug and a bent valve on #3 cylinder.