2004.5 SP700 EFI ... Losing Coolant?
I've had the very same problem with a 03 600 Sportsman and thought originally that it was the head gasket as there were air bubbles rising in the rad with the cap off when the bike was running which indicates air under compression being forced into the antifreeze. So, I tore the bike down but could see no evidence of a leak on the head gasket. I went deeper and replaced the base gasket which certainly looked like it could have been the culprit as it was saturated and mushy. I put the bike back together and at the same time I tightened the bolts holding the water pump cover as well. After this the problem seemed solved for about 100 miles at which time the leak came back after a long agressive ride. So, I tore it down a second time and this time I took the head into a machine shop to find that the head was not flat. I wouldn't say it was warped as what it showed with a straight edge was that the area around the one upper right bolt hole protruded higher than the edge of the cylinder. If you look at it the area between the cylinder and the first cooling port is only about 1/4 inch in this area. The guy at the machine shop (who builds racing engines as well) said that this was definately my problem with the antifreeze leak. I had him plane the head and he took off 3 thousands. The book reads that the tolerance for warpage is 4 thousands so again I had my doubts if the head could have been the problem. Since I had the head off anyway I again replaced the base gasket and this time used ultra grey sealing compound on the base gasket to help the gasket seal. I put the bike together again and this time, so far, granted I only have about 30 miles on it, it hasn't leaked a drop.
I had a dealer swear to me that the head gasket wasn't the problem (without seeing the bike). He claims that the problem in his experience is always the water pump seal. Myself I can't see it because by design the water pump seal leaks externally by way of a weep hole in the bottom of the water pump housing. The water pump housing gasket could leak internally but only by way of one port that allows the antifreeze into the engine.
Hope this helps. If you find out anything, let us know.