Surging problems

Hi,

I have a Honda HRX217 mower that just recently began surging. When it's cold and the autochoke is closed, it runs fine. As soon as it warms up, I can verify the choke opens and it begins surging. A tiny bit of common sense (which is all I have) tells me it's not getting fuel and that it needs a carb cleaning but what I don't understand is that as soon as I engage the blade, it runs fine. I can't see the throttle surging nor hear it. It cuts and rolls along wonderfully until I release the blade clutch, at which point the problem returns. It's worse/stalls when the throttle is moved to idle. I tried searching the forum and didn't see anything with the exact symptoms (more often the problems seem to come with the load and not without from my quick searches).

Am I overlooking something obvious? Normally I'd guess something is plugging one of the jets in the carburetor but I don't want to ignore symptoms and miss something obvious and I don't want to go all gorilla on this mower if I can avoid it.

Thanks for any help.