When I first removed my fork the split compression ring was tight and the fork remained on the frame when the stem was removed.
Now when I tried to reinstall the split compression ring, it does not seem to compress enough to keep the fork in place.
What is the trick on getting the ring to go all the way inside the bearing?

The headset is a FSA No 42/ACB

[QUOTE=chibi;18550302]What is the trick on getting the ring to go all the way inside the bearing? [QUOTE]

Tension. When you put proper tension on the headset using the top-cap bolt, that is what pushes everything together. Here's a link to a video on headset adjustment that might help:

https://www.youtube.com/watch?v=W2RHkdRePa8

Thank. I understand the top bolt pushed everything together. Just curious why the fork stay put when I first took it apart. Like the compression ring was tigher before.

It's common for the compression ring to stick to the fork's steerer both during removal as well as in installation sometimes. Corrosion, grit and with carbon steerers a necking down of the steerer from previous ring pressure all can make the ring not play nice. Andy.