Lol, rusty, I'm cheap. I'm not gonna spend time and $$ nitpicking for a 1/20 of a hp loss. My bike is very fast with beaucoup power, just like I need it. I could spend $90 for a custom sprocket from King's. However, the guy never returns my pm's or emails, so no loss. If I DID buy the sprocket, install it and the problem STILL exists, I'm out $90. I COULD buy another $20 Chinese sprocket, but that one could be out of round too. It COULD be a slightly bent bottom cartridge, or it COULD be a defective $10 freewheel. I have a $70 freewheel for my next build. If the 'wheel fails, I MIGHT install the expensive freewheel.
Nah, I'll just screw on another cheap, used freewheel and keep riding it to work daily, like I've been doing for the past 6 months. :
Hey! If the failed 'wheel IS the culprit, then I will have fixed the problem and regained the hp loss...for free!