Cold start problems -96 F650F
 

A week ago I helped a friend to change the intake manifold (between carbs and cylinder). We also changed the airfilter and when everything was assembled the bike started and ran nice. This was in daytime and the temperature was maybe 15°c.

The next morning the owner tried to start the bike but the only way to start it was not to use a choke and run it on the starter for a long while. When it starts it's possible to use the choke again but it's running rough. When the bike is hot it's running normal.

Any ideas?
Thanks