2024-06-15 Scotch Carb Rebuild Link

The carbs have been thoroughly cleaned now. Starting with a preliminary boiling (5 to 1 lemon-juice)for a full day which removed most of the grease, oil and some light varnish and scaling. The body, bowl and top-cover were then glass-bead cleaned (I have a blasting cabinet); with one exception. I DID NOT glass-bead the throttle-bores!
The throttle-plates are precision ground to fit the venturi tightly when closed. Any attempt to clean the venturi or the throttle-plates by glass-bead cleaning would ruin them by destroying the ground edge of the throttle-plates. This would make tuning and sync'ing all but impossible. The varnish was removed from the venturis and plates with a small paint brush,lacquer-thinner and a light rubbing with "Scotch-Brite". For similar reasons the slide-bores and needle-pistons were left alone with only a cleaning using lacquer-thinner and a soft cloth.
Also note the last pictures regarding the choke pick-up tube. I was lucky in finding the jet when it blew out under air-pressure cleaning. A heavy towel on my work-bench caught it and saved me a lot of additional work! I suspect the tiny split may have been from years of stress from the jet being pressed into the end. This jet is critical! Without it there is no metered flow of fuel to and through the choke passages.
The final check to assure clear-flow through all the passage ways will be done with lacquer-thinner (to dissolve and flush anything remaining in the galleries) using the syringe you saw in the previous pictures. Once confirmed flowing and clean the final polishing and painting can take place.
The Philips-heads of 2 of the carb-bowl drain-screws were in rough shape and I dislike Philips-heads anyway, so I silver-soldered a socket-head onto them. The idle-air screws will receive a similar treatment.