When cold
 

Guys some idea why the motorcycle lose some power when the weather is cold , when i go to work in the early mornings , but when is warm , about 8, 10 deg C is ok ? Seems like a stalling when i open the throttle ?

You may have some water in your fuel. You might try adding some Seafoam or other fuel enhancers.

You may also want to let the bike warm up a little longer so that it is running smooth without any choke.

tnx alot again ! :S

Let me know if that helps. If not, you might want to check the diaphragm in your petcock. It could have a small tear or hole.