cooling issues…again

Hey everybody. i was hoping to pick your brains, as i have already tried all my area dealers. i have been having an issue with my 08 650 outty. the coolant keeps puking out of the overflow. i was told a bad head gasket would cause this and to do a pressure test which i had done and showed it to be fine. so i replaced the t-stat, thinking it might be the next logical choice…to no avail. whenever i first start riding, just before the fan kicks on for the first time, it pukes out whatever is in the overflow bottle. it did it once more just before the fan kicked on a second time, then for the rest of the ride was fine. checked the level in the rad when i got home and it was down about an inch. i left it alone. thought maybe i had just overfilled it….but then it did it the next ride. it just does it at the beginning of the ride then everything is normal. any ideas? could it be as stupid as a bad cap? i should probably tell you i have the rad mounted on the front rack(BRP kit) so i can see how much is flowing back and forth between the rad and overflow. when i first start riding and it starts warming up, its almost a freeflow into the resi, then it squirts out, fan kicks on and it stops. then it goes back and forth like normal. i’m supposed to go on a 3 day camping trip soon and need to get this resolved. any input would be helpful. thanks