are you serious??
if your engine has a regular clutch just pull it in and stop the bike...the engine will stay running if the carb ius adjusted right.
if you have a centrifugal clutch, just stop the bike and the clutch should slip so the engine stays running when the bike is at a stop.
if your engine won't idle when you pull in the clutch to stop, you have the idle screw turned out too far or the clutch is WAY out of adjustment.
try screwing the idle screw in...tighten it(on the left side of the carb) until the idle comes up and the engine stays running.
your engine should idle like this without the bike moving.
Mine will sit and idle until the gas tank is empty.
http://www.youtube.com/watch?v=Ry-Sjb_HQao