After picking up my brand new 1977 CB750A (1637 miles!!) on Saturday, I began testing the electrical system. Everything seems to be working quite well with the exception of the flasher relay (easy fix) and the parking switch at the rear brake pedal.
I thought someone may be interested in how I'm repairing my switch. After trying to clean it by simply spraying some clear down through the plunger, I determined that wasn't going to work. I really wanted to keep the original function of this switch, so I thought about how could I repair it. I looked at the switch and realized that if I cut around the diameter of the non-threaded portion of the housing, I should be able to split it and access the contacts to clean them. I took my Dremel with a cutting disc and cut around the barrel of the switch and split it open.
Good news! It did have a small amount of corrosion inside, but easy enough to clean. The spring looked a bit rough, so I removed it and replaced it with a slightly modified spring from a Pilot gel pen. It was almost the perfect size. I cleaned the contacts and the plunger, applied some dielectric grease and held the 2 parts together for testing. It works.
Now I'm in the process of holding it together while aligned properly and applying JB Weld around the outside to put it back together. It will be covered up by the rubber boot, so no one will even notice. I'll get some pictures this evening before final assembly to show the work and what's inside.