My gas engine is running fine at high speed and there is no hesitation from idle to high but after idling for about a half minute the idle became slower and slower until the engine stops.What could be the problem

My Zenoah G23 did something similar to what you describe. I took the carb apart and gave it a good cleaning, and the problem went away.

My guess is that your low speed needle is a little rich and over time the engine gets bogged down. Try leaning a little and see what happens

Your low needle is to rich, the engine can't burn all the fuel it's getting so it slowly loads upmaking it go slower and slower until it drowns itself out and dies. Turn the low needle clockwise about 1/8 of a turn at a time, test your transition and idle each time you make a change. Keep going leaner until the engine won't transition well, then go back richer just until it will transition smoothly, reset your idle speed and fly.

http://www.rcaerobats.net has some good stuff on gas carbs and tuning, worth a read.

I agree with both above, probably a rich idle, also cleaning the carb won't hurt anything especially the fine screen filter. Make sure you're filtering on the gas can/pump line and using an inline filter between the tank and carb.


EDIT: Edited to fix link

Andy, the website comes up but there is nothing on it.

Look at this procedure. It's always worked for me

http://tech.flygsw.org/walbro_tuneup.htm

.com .net whats a simple typo between friends

Thats the same article thats linked to on rcaerobats among a couple of others, so I agree, good stuff!


And just for the record, TGIF!!! Can't wait to get out of the office and fly tomorrow!