I went out this morning and opened the radiator up to see how full it was (burped the system 3 times several months ago). The radiator was low enough that I could not see any coolant and the resevoir was a bit overfull. I stood the bike up straight and opened the resevoir cap until the radiator was full once again and closed everything back up. The resevoir level was back at the juuuuust below full mark which is where it was when I last burped it. So, for me this is proof that my radiator cap is only letting coolant go out of the radiator when it gets warm and never returns when it cools down. Per AUS_TR650 recomendation, I will be looking to purchase a KLX radiator cap soon and see if after several heat cycles (long-ish rides) the new cap allows the coolant to return to the radiator. Kev.
Just to throw more information out there... I have not been having any problems (knock on wood) with overheating to date (1000+ miles). When I opened the radiator cap a couple weeks ago just to see, I noticed that the overfill tank seemed to drain immediately into the radiator and started overflowing. I put the cap back and left it alone. I find it interesting that some have to actually open the overfill cap to get it to flow. Could the overfill cap vent be plugged up or something on those with problems? Just a thought, which doesn't really make much sense, but who knows.
I was enroute to the house from work (a short blast on the Interstate of 70 - 75 mph and got to a surface street that was backed up. Up ahead I could see police activity and they had the streets blocked off. Traffic was funneling only right and left and by normal traffic light - so... I sat and slowly moved up. Outside temp was in the mid 90's. After about three interations of the lights changing, my temp guage pegged and my LED was blinking. I was finally able to get it moving again after I made it through the light but it just didn't seem like it was sitting long enough to peg the bars and start the light flashing. I'm going to try and 'burp' it and see if that helps.
If the temp gauge came back down after you started rolling along and it didn't overflow out the reservoir, I suspect ambient conditions were the cause of overheating and your system is okay. I'm not looking forward to my first summer where temps get 100 deg F+ when commuting in traffic.
If the caps on these things are 16PSI or so, if the cause was that the vent was blocked, the blockage would have to be resistant to 16PSI or whatever the resistance on the cap return valve is, wouldn't it? It just seems to me that the pressure difference required to force the springs in the radiator cap to move would surely be enough to overcome any unintended vent blockage.
