Well, my guess is the cleaner is reducing the combustibility of the gasoline to some extent. This would mean the air:fuel ratio is set too rich in the carb, and when you add the cleaner it brings the ratio into line. (If I'm thinking this correctly...)
I think the main jet is the port visible looking straight up in the center of the float bowl, accessible only by removing the bowl. Some are screw in jets, others pressed in.
I'd take the bowl off, and unscrew that jet. Clean it with a small piece of wire, being careful not to damage it or make the hole bigger. I'd also spray some carb cleaner up the passage where that jet came out.
While I was at it, I'd GENTLY seat any adjustable jets, CAREFULLY COUNTING the exact number of turns (to the 1/16 turn) that it took to seat the jet, and writing this down. Then I'd back the jets out completely, and clean both it and the port it came out of with the spray cleaner. Then reinstall the jet, GENTLY seating it, and backing it back out the previously determined number of turns.
Barring this, I dunno... Wait for an expert to chime in.