Thanks for the quick answer. I did clean up the pilot nozzle (orifice) as much as I can with a brush even though I am not sure if that is the isue. Few things I noticed on the pilot opertaion.
1. No problem if I set the switch in pilot mode. Pilot will stay on overnight. Problem comes after setting switch to ON mode overnight. Typically, pilot will be off after a hour or so after a batch of water is heated up.
2. Thermouple is covered by pilot flame. The flame color is blue as fas as I can tell.
3. Without any new suggestion from experts, my next choice will be gas valve. The problem with gas vavle is Kennmore will not sell gas valve only. They sell whole burner assembly, $300. Half the price of a brand new unit. The unit I have is 18 months new.
4. I tried web to locate a Robershaw 64-LC4-376 gas valve (Unitrol) without any success. Do you know where to get one ?