Originally Posted by
fietsbob
NB : the top cap is also what adjusts the headset bearing preload,
the clamping of the stem round the steerer tube is what holds that bearing adjustment .
so as you remove both you must re adjust the headset again before the job is done,
after you put a different stem on the fork.
Don't think so in this case. Can't be 100% sure from the close in photo, but I think he has a fatty headshok.
If so, that top cap will be either a damper contol or a lockout switch depending on which model.