Blue smoke on cold engine startup.

I had my engine (topend) rebuilt about 9 months ago. New piston, valves ect. all the good stuff. I broke it in nice and easy and it runs great. I have a 125 main, the needle dropped down 1 notch and a 40 pilot. After about the 3rd month after the rebuild (I would say about 10 hrs on the motor) it is blowing out blue smoke ONLY when I start it up when the motor is cold. It only blows blue smoke for about 10 to 15 seconds and then stops and does not ever do it again until I leave the motor off like overnight. Any ideas? Valve seals? Will this cause any damage? I think I have a one year warranty on the rebuild.

Thanks.

it's the valve seals nothing major mine does it but i'm haveing the head ported and the seals replaced right now so hopfully it will put and end to that it's just where when it sits overnight the oil is pulled above the exhuast valves and it will slowly seep down into the exhaust port it's somthing i wouldn't worry about until the next time you tear into the motor unless it gets worse and starts burning oil while it's running too, then i would replace them