F50 2003 Stumble cold start

[gfl]

This motor has been bullet proof for 6yrs. Other than a bad coil recently, I have had no problems.
The problem that has surfaced now , is on a cold start. It will start up with the turn of the key and idle high for about 10seconds then falls back to curb idle prematurely and stumbles and will stall if I don't raise the throttle manually.
After a minute or so once warmed up it is fine. Start and run great on one turn of the key the rest of the day.
Just bought a mamometer and will ck. the carbs hopefully today. I understand about dirty carbs, but it is the middle of the season and it is in the water and if it comes down to that , I'll wait till the offseason to clean them. I can live with manually raises the throttle on cold start if I have to.
But the thought of a temp sensor and Prime start solenoids and CDI unit,
makes me want to go deeper.
Could anyone give me a plan of attack for the quik fix?

[99yam40]

I believe lifting the idle lever or advancing the throttle with the key on will disable the automatic advance of the timing during warm up,but not sure on your F50.
Also normally the motor timing should stay advanced during warm up until a temp switch tells it it is warm, but that may be the old way/ A timing light should tell you what is going on. You can pull and test switch in water as you heat it