As reported several times, Sunny the Sunbeam has not been running well. When he first came off the truck, the idle speed was close to 3000 RPM, well above the
800 RPM suggested in the workshop manual. After some fiddling, I was able to bring the idle speed down to 1500 RPM, but the engine seemed to be running too rich. The spark plugs were black and sooty, and the exhaust smelled like gasoline. The garage carbon monoxide detector confirmed the problem, even with the garage doors open. For reference, the WRX powered 818 car never caused the detector to go above 0, even with the doors closed. My thanks to Arnold, who urged me to install a carbon monoxide alarm in the garage.
It was clear that Sunny had a problem with incomplete combustion. In the previous post I mentioned the colortune tool, which allows one to look inside of an engine’s cylinder while it is running and see the color of the flame when
the gasoline-air mixture is ignited. Why is the color of the flame important? It turns out that a yellow flame is indicative of incomplete combustion and the presence of carbon monoxide and unburned gasoline. In other words, a yellow flame means that too much gasoline is entering the cylinders relative to the air (oxygen) available to burn.
The picture above and on the left shows the color tune tool from the side. You can see the threads that screw into into the engine’s spark plug hole. The spark plug wire connects on the top, as with a normal plug. The picture on the right is a view from the top; you can see the color of the notepaper shining through the glass on the right side of the tool, between the inner core and the nut on the outside. 
I inserted the colortune in cylinder #1 and started the engine. I was surprised to see anything at all since Robert mentioned that the tool was difficult to use. But there was a clear yellow flame that confirmed the sooty spark plugs and the reading on the carbon monoxide alarm. I adjusted the mixture screw on the front carburetor and, after a few tries, saw the blue flame. I repeated the process on cylinder #4 and the rear carburetor. Sunny runs much better: the idle speed is now close to the recommended figure, and the exhaust no longer reeks of unburned fuel.
Sunbeam 