I've managed to get both my stock carbed 650s dialed in for a pretty consistent 1100-1200 RPM hot idle speed. Yes, a small idle speed adjustment is sometimes needed between hot summer running and cooler spring or fall running, but it's just a minor tweak, maybe 1/4 turn at most on the idle speed screw either way. It does take some tinkering to get the speed just right, fast enough so it won't stall cold but not run too fast once hot, but it can be done. I have BS38s on one and BS34s on the other. Both idle nice.