During the winter my radiator started leaking. Being proactive I changed out the thermostat, water pump, heater core, rad lines, and heater hoses. I was driving from Northern PA to the East side of D.C. 3 weeks ago and it started getting hot. I stopped and felt the upper rad hose had a lot of pressure on it. I changed the thermostat. That was about halfway through my trip. When I got to D.C. I had talked to a friend and he told me to check the fan clutch. It was bad so I changed that out. The new thermostat was bad as well. I pulled it out and it wasn't opening all the way until I jammed a screwdriver and pried on it, I felt it give and it opened all the way up. So, I put another new one in. Anyway if I sit and let it idle it will not over heat unless I turn the A/C on. If I am driving on the highway 70-75 mph with the heat on it will run around the far side of the m and sometimes into the a in normal. I have to watch my speed and adjust as I am going to keep it reasonable. I have used the chemical set from Fisher's Auto to see if there was any carbon monoxide in the water and it is not showing any. So I assume I don't have a bad head gasket but I don't feel I can rule it out, since it may be blocking some water passages. I have not flushed the system so there could be build up in the block as well. I have been on travel for work for the last 3 weeks so I haven't been able to do too much to it. I am going to limp home this Friday and see if I can either find time to work on it Friday/Saturday or drop it off at the local shop and ride my bike back down here. Any ideas on how to troubleshoot this problem better?