While synchronizing my carbs for the upcoming year, I noticed that I would sometimes get an intermittent drop in vacuum pressure in cylinder #3. The pressure would drop but then almost instantly recover. There is no rhyme or reason when the drop happens and is not tied to a certain event. If I put my palm against the carb body it pulls a vacuum against my palm and the slide is working so that's not the problem.
I just cleaned the carbs so I don't think it's an issue with dirty carbs. This seems to indicate a sticking valve to me. Figured I would try some Marvel Mystery Oil since that's helped with valve problems on other projects in the past. If that doesn't help I'll pull the valve cover and investigate. I changed a few shims over the winter and didn't notice anything weird while doing the maintenance.
Does anyone have any other suggestions?
