Rusty, I don't think you need to get into a new carburetor. The 4.9% CO is pretty lenient, and it sounds like they ran the test properly. Did the inspector let the speed stabilize before taking the reading? That is usually under computer control, so as to prevent any manipulation of test results, but a brief acceleration at just the right time during the test might have gotten the accelerator pump discharge involved in the reading. That shouldn't happen, but depending on how the sample system is timed and programmed, it is possible. What CO level did you get at idle speed?
Possibilites for your condition are: restricted air cleaner, choke not fully off, float level is too high (good possibility), main metering jet is too large (possible, but not the first thing to get into), carburetor base gasket is improperly installed, or is the wrong gasket. Either situation with the gasket will block the vacuum passage to the metering rod piston, which will keep the metering rod in the rich position, and would put the CO in about the 6% range.
With "fuel change," I'm assuming you mean regular or high-test gasoline. No, that won't help. There is something going on with your carburetor.
Harvester
