I did some work today to add a second set of vacuum taps to the Honda Pacific Coast PC800 carburetor that I have modified into fuel injection throttle bodies as part of my long-running fuel injection conversion project. In this photo you can see two metal pipes penetrating the lower portions of the throttle bodies. These pipe taps will act as vacuum taps. I am going to hook either the Manifold Air Pressure (MAP) sensor or an Idle Air Control (IAC) valve to these taps. The other existing factory-installed taps will be used for the MAP or IAC that isn’t plugged into the new set of taps.
Here’s the finished view with vacuum hose hooked to the new taps and the new tapx shaved flush in the throttle bodies.
My finger is pointing to the new tap.
All in all, it was a pretty clean installation. I used JB Weld to hold everything together. Hopefully the 10% ethanol gas that we get everywhere in the USA won’t someday degrade all of the JB Weld that holds together the throttle bodies.
The throttle bodies installed on the bike. Lots of hoses and wires running everywhere to make this bike come alive! Up next is figuring out how to make the MAP sensor not flutter all over the place (vacuum reservoir) and finally figuring out how to do proper idle air control using an IAC that works with my existing MicroSquirt setup. The engine really needs IAC so that it will properly start when the engine is cold.