even when my choke is on, my 300ex is real hard to start when cold, any idea's??????

 

You might try a litle fatter pilot jet than what you run now. One size fatter might help if there in no other problem.

 

More than likely it's what he just said, improper jetting for the temp.
BUT i just want to make sure...
This may sound dumb, but you aren't giving it any gas when you are trying to start it are you? If you are that could be your trouble.
One other thing. 300ex's have a "drain" screw on the side of the quad toward the center of the frame which is basically a fuel drain. What happens is that your gas can become "stale" in no time at all and it can make it really hard to start....especially when it's cold.
After my quad sat for a week and a half i had to open the drain screw just for a second to drain a little of the old gas in the line out and it started right up!
Mike