- Gave the larger carb parts a gentle brush over, inside and out, with Gunk Green degreaser. This did a good job of removing the majority of the dirt from the outer surface and leaves a matte finish.
- Sprayed the jets, accelerator pump and passageways through with carb cleaner
- Checked the plastic balls in the accelerator pumps to ensure they move freely. One was sticking, even after washing, so I unscrewed the pump's cap (that's the part with the four holes on top, not pictured here) using circlip pliers to hold it. Inside, everything looked gum-free so I just re-assembled it with a little less torque and that seemed to do the trick.
- Tackled the corroded choke plunger bores - a finicky job! I suspect galvanic corrosion from years of brass-on-aluminium contact left a thick oxide layer behind. Fitting new plungers would have been impossible without removing that so I fashioned a scraper tool from a circular, Dremel-type engraving bit and a handle from a camera lens spanner. About 10 minutes of work per carb was enough to get the old plungers in without too much sticking. From there, I switched to using the plungers themselves, coated in metal polish, to smooth the new surface. I used a metal rod to repeatedly push down from the top and a small allen key (thin enough to fit through the nozzle hole) to push back up from the bottom.
Technical Notes & Learnings
You can find a handy parts diagram for the VHB-30 carbs on Gregory Bender's site.