Cold start fast idle cam sets cold start high idle level to keep cold engine lit.
You can adjust it down...look for a manual for the carb online, it will show you the screw to turn out...if its an electric choke, you must allow it to cool down before it can be set again...
Your surging issue could be a lot of things...sounds like fuel supply loss of pressure ...starting at the fuel tank...could be clogged strainer on the pickup, split pickup tube in tank, crushed fuel supply line, bad fuel pump, bad settings on carb float level...
Other possible causes, retarded cam action due to bad timing chain/gear, bad ignition timing, weak valve springs...your surge may be valve float...
Have fun my friend...
