The "compensator" is a combination of a cap for the metering diaphragm and a matching air filter where the vent for the diaphragm leads to the inside of the air filter instead of the (typical) outside. The result is that the diaphragm is using the same atmospheric pressure as the intake side of the carb, thus taking the filter condition mostly out of the "equation". When the air filter becomes dirty, as they all do, the fuel metering characteristics won't change as drastically that way. A clogged filter will still rob power-producing capability from the engine, this feature is not intended to overcome that, but it does make it so you don't have to continually adjust the adjustable needles to maintain the optimum mixture during the process.
The same effect is obtained if you don't use an air filter or if the carburetor is located fully inside the filtered airbox.
I've known otherwise for a while now, but the non-pro 026 is supposed to have full adjustability if the common claim here is to be believed.
Glen
