HI:
For those of you that have Webers(side draft) pay attention to a small part called "Pump Demand Valve Ball".
It's a 4mm ball(acts like a ball check) that is involved with the "pump circuit".
I did a rebuild on a 45 that is presently on the car and found that one of these"balls" were corroded into place.
I will replace both with stainless steel ones as the chrome jobs in there now are susceptible to this issue.
The same type of thing happened to an old Honda I have(Black Bomber) which had a similar arrangement for its oil pump(no oil pressure was the result).
Any time I see ball checks that can be in a corrosion situation I replace them with SS.
May this tidbit of info help someone one day!!
