Vetlpc, let's start at the begin. Have you read the starting procedure as described in the Owner's Manual?
https://www.honda4fun.com/dwnload/Owners-Manual/CB500-K1-Owners-Manual.pdf Every owner of a CB500 is advised to read carefully the starting procedures.
Pay extra attention to STARTING IN EXTREME COLD WEATHER in the CB500 Owner's Manual p.29.
Whenever my CB500 has stood for four days or longer, I need this procedure. The reason we need this more than back then, lies in the changed properties of gasolines.
Then this: as far as our model, one is not supposed to start riding with the chokes still (partially) closed. Honda wanted you to have both hands at the handlebars at all time. To compensate, you start riding with a somewhat raised idle. Some achieve this by keeping the throttle grip somewhat inward, as the Owner's Manual suggests, others find it easier to turn the idle adjuster knob (under the tank) somewhat to raise the idle, after a mile or so, they readjust that knob, say at a traffic light or so.
BTW, when the engine is warm enough, I recommend an idle of minimum 1150 rpm at all time.
